Algebraic Solution: Solve using the substitution method

Examples with solutions for Algebraic Solution: Solve using the substitution method

Exercise #1

Solve the following equations:

{x+y=18y=13 \begin{cases} x+y=18 \\ y=13 \end{cases}

Video Solution

Step-by-Step Solution

To solve the system of equations using substitution, follow these steps:

  • The system of equations given is: {x+y=18y=13 \begin{cases} x + y = 18 \\ y = 13 \end{cases}
  • Step 1: Extract the given value for y y from the second equation: y=13 y = 13 .
  • Step 2: Substitute y=13 y = 13 into the first equation: x+13=18 x + 13 = 18
  • Step 3: Solve for x x by subtracting 13 13 from both sides of the equation: x=1813 x = 18 - 13
  • Step 4: After the subtraction, we find: x=5 x = 5

Therefore, the solution to the problem is x=5 x = 5 and y=13 y = 13 .

Answer

x=5,y=13 x=5,y=13

Exercise #2

Solve the following equations:

{2x+y=9x=5 \begin{cases} 2x+y=9 \\ x=5 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system of equations, we'll use the substitution method as follows:

  • Step 1: Identify the given information.
    We have two equations: {2x+y=9x=5 \begin{cases} 2x + y = 9 \\ x = 5 \end{cases}
  • Step 2: Substitute x=5x = 5 into the first equation.
    The equation becomes: 2(5)+y=9 2(5) + y = 9 which simplifies to: 10+y=9 10 + y = 9
  • Step 3: Solve for yy.
    Subtract 10 from both sides: y=910 y = 9 - 10 y=1 y = -1
  • Step 4: Verify the solution.
    Substituting x=5x = 5 and y=1y = -1 back into the first equation confirms the solution:
    2(5)+(1)=101=9 2(5) + (-1) = 10 - 1 = 9

Both equations are satisfied with x=5x = 5 and y=1y = -1.

Therefore, the solution to the system of equations is x=5,y=1 x = 5, y = -1 .

Answer

x=5,y=1 x=5,y=-1

Exercise #3

Find the value of x and and band the substitution method.

{x+y=52x3y=15 \begin{cases} x+y=5 \\ 2x-3y=-15 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system using the substitution method, we'll follow these steps:

  • Step 1: Solve the first equation for one variable.

  • Step 2: Substitute this expression into the second equation.

  • Step 3: Solve for the second variable.

  • Step 4: Use the value of the second variable to find the first variable.

Step 1: Solve the first equation x+y=5x + y = 5 for yy.
We have: y=5xy = 5 - x.

Step 2: Substitute y=5xy = 5 - x into the second equation 2x3y=152x - 3y = -15.
This gives us: 2x3(5x)=152x - 3(5 - x) = -15.

Step 3: Simplify and solve for x x :
2x15+3xamp;=155x15amp;=155xamp;=0xamp;=0. \begin{aligned} 2x - 15 + 3x &= -15 \\ 5x - 15 &= -15 \\ 5x &= 0 \\ x &= 0. \end{aligned}

Step 4: Substitute x=0x = 0 back into y=5xy = 5 - x to find yy.
yamp;=50yamp;=5. \begin{aligned} y &= 5 - 0 \\ y &= 5. \end{aligned}

Thus, the solution to the system of equations is x=0x = 0 and y=5y = 5.

The correct answer from the list of choices is: x=0,y=5x = 0, y = 5

Answer

x=0,y=5 x=0,y=5

Exercise #4

Find the value of x and and band the substitution method.

{x2y=43x+y=8 \begin{cases} -x-2y=4 \\ 3x+y=8 \end{cases}

Video Solution

Step-by-Step Solution

Let's begin by solving the system of equations using the substitution method.

First, solve the second equation for yy:

3x+y=83x + y = 8

Solve for yy:

y=83xy = 8 - 3x

Next, substitute this expression for yy in the first equation:

x2(83x)=4-x - 2(8 - 3x) = 4

Distribute the 2-2:

x16+6x=4-x - 16 + 6x = 4

Combine like terms:

5x16=45x - 16 = 4

Add 16 to both sides:

5x=205x = 20

Divide by 5:

x=4x = 4

Now, substitute x=4x = 4 back into y=83xy = 8 - 3x to find yy:

y=83(4)y = 8 - 3(4)

y=812y = 8 - 12

y=4y = -4

Therefore, the solution to the system of equations is (x,y)=(4,4)(x, y) = (4, -4).

Thus, the values of xx and yy are x=4x = 4 and y=4y = -4.

Answer

x=4,y=4 x=4,y=-4

Exercise #5

Find the value of x and and band the substitution method.

{5x+9y=18x+8y=16 \begin{cases} -5x+9y=18 \\ x+8y=16 \end{cases}

Video Solution

Step-by-Step Solution

To solve the given system of linear equations using the substitution method, follow these steps:

  • Step 1: Solve the second equation for x x .

From the second equation:

x+8y=16 x + 8y = 16

We can solve for x x as follows:

x=168y x = 16 - 8y
  • Step 2: Substitute the expression for x x into the first equation.

Substitute x=168y x = 16 - 8y into the first equation:

5(168y)+9y=18 -5(16 - 8y) + 9y = 18

Simplify and solve for y y :

- Distribute 5-5:

80+40y+9y=18 -80 + 40y + 9y = 18

- Combine like terms:

49y80=18 49y - 80 = 18

- Add 80 to both sides:

49y=98 49y = 98

- Divide by 49:

y=9849=2 y = \frac{98}{49} = 2
  • Step 3: Substitute y=2 y = 2 back into the expression for x x .

The expression for x x is:

x=168y x = 16 - 8y

- Substitute y=2 y = 2 :

x=168(2) x = 16 - 8(2) x=1616 x = 16 - 16 x=0 x = 0

Therefore, the values that satisfy both equations in the system are x=0 x = 0 and y=2 y = 2 .

Answer

x=0,y=2 x=0,y=2

Exercise #6

Find the value of x and and band the substitution method.

{4x+4y=152x+8y=12 \begin{cases} -4x+4y=15 \\ 2x+8y=12 \end{cases}

Video Solution

Step-by-Step Solution

To solve this problem, we'll apply the substitution method, following these steps:

  • Step 1: Solve the first equation for one of the variables.
  • Step 2: Substitute this expression into the second equation and solve for the other variable.
  • Step 3: Use the value found in Step 2 in the rearranged first equation to find the remaining variable.

Step-by-Step Solution:

Step 1: By using the first equation, 4x+4y=15-4x + 4y = 15, we can solve for y y .

Step 1.1: Simplify the equation to solve for y y by adding 4x 4x to both sides:
4y=4x+15 4y = 4x + 15

Step 1.2: Divide every term by 4:
y=x+154 y = x + \frac{15}{4}

Step 2: Substitute the expression for y y into the second equation, 2x+8y=12 2x + 8y = 12 .

Step 2.1: Substitute y=x+154 y = x + \frac{15}{4} :
2x+8(x+154)=12 2x + 8(x + \frac{15}{4}) = 12

Step 2.2: Simplify and solve for x x :
2x+8x+30=12 2x + 8x + 30 = 12

Combine like terms:
10x+30=12 10x + 30 = 12

Subtract 30 from both sides:
10x=1230 10x = 12 - 30

Resulting in:
10x=18 10x = -18

Divide by 10:
x=95 x = -\frac{9}{5}

Step 3: Substitute x=95 x = -\frac{9}{5} back into the expression for y y :

y=95+154 y = -\frac{9}{5} + \frac{15}{4}

Convert fractions to a common denominator, which is 20:
y=3620+7520 y = -\frac{36}{20} + \frac{75}{20}

Solve by combining terms:
y=3920 y = \frac{39}{20}

Thus, the solution to the system is x=95 x = -\frac{9}{5} and y=3920 y = \frac{39}{20} .

Therefore, the correct solution is identified as choice 4.

Answer

x=95,y=3920 x=-\frac{9}{5},y=\frac{39}{20}

Exercise #7

Find the value of x and and band the substitution method.

{5x+y=83x2y=11 \begin{cases} -5x+y=8 \\ 3x-2y=11 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system of equations using the substitution method, we follow these steps:

  • Step 1: Solve for one of the variables in terms of the other using the first equation 5x+y=8 -5x + y = 8 .
    • We solve for y y :

    y=5x+8 y = 5x + 8

  • Step 2: Substitute the expression for y y from Step 1 into the second equation 3x2y=11 3x - 2y = 11 .
  • 3x2(5x+8)=11 3x - 2(5x + 8) = 11

  • Step 3: Simplify and solve for x x .
  • Simplify the substitution:

    3x10x16=11 3x - 10x - 16 = 11

    7x16=11 -7x - 16 = 11

    Add 16 to both sides:

    7x=27 -7x = 27

    Divide by -7:

    x=277 x = -\frac{27}{7}

  • Step 4: Substitute x x back into the expression for y y from Step 1.
  • y=5(277)+8 y = 5\left(-\frac{27}{7}\right) + 8

    Simplify:

    y=1357+567 y = -\frac{135}{7} + \frac{56}{7}

    y=1357+567=797 y = -\frac{135}{7} + \frac{56}{7} = -\frac{79}{7}

Therefore, the solution to the system is x=277 x = -\frac{27}{7} and y=797 y = -\frac{79}{7} .

Answer

x=277,y=797 x=-\frac{27}{7},y=-\frac{79}{7}

Exercise #8

Choose the correct answer for the following exercise:

{x+y=152x+2y=12 \begin{cases} x+y=15 \\ 2x+2y=12\frac{}{} \end{cases}

Video Solution

Step-by-Step Solution

To solve the system of equations, follow the steps below:

  • Simplify the second equation: Start with 2x+2y=12 2x + 2y = 12 . Divide every term by 2 to simplify it to x+y=6 x + y = 6 .
  • Compare the two equations now: x+y=15 x + y = 15 and x+y=6 x + y = 6 .

Consider these equations:
Since both are simplified to the form x+y=constant x + y = \text{constant} , they describe two parallel lines, given that they have the same coefficients of x x and y y but different constants (15 and 6).

Parallel lines never intersect. Thus, there is no solution for this system of equations, as they represent two distinct parallel lines.

Therefore, the correct answer is: No solution.

Answer

No solution

Exercise #9

Find the value of x and and band the substitution method.

{8x2y=103x+3y=9 \begin{cases} 8x-2y=10 \\ 3x+3y=9 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system of equations using the substitution method, follow these steps:

  • Solve 3x+3y=9 3x + 3y = 9 for y y :

Divide the whole equation by 3 to simplify:
x+y=3 x + y = 3

  • Express y y in terms of x x :

y=3x y = 3 - x

  • Substitute y=3x y = 3 - x into the first equation:

We substitute into 8x2y=10 8x - 2y = 10 :
8x2(3x)=10 8x - 2(3 - x) = 10

Simplify and solve for x x :

8x6+2x=10 8x - 6 + 2x = 10
10x6=10 10x - 6 = 10
Add 6 to both sides:
10x=16 10x = 16
Divide by 10:
x=1610=85 x = \frac{16}{10} = \frac{8}{5}

  • Substitute back to find y y :

Use y=3x y = 3 - x :
y=385=15585=75 y = 3 - \frac{8}{5} = \frac{15}{5} - \frac{8}{5} = \frac{7}{5}

Therefore, the solution to the system is x=85 x = \frac{8}{5} and y=75 y = \frac{7}{5} .

Answer

x=85,y=1410 x=\frac{8}{5},y=\frac{14}{10}

Exercise #10

Find the value of x and and band the substitution method.

{x+4y=53y2x+3y=6 \begin{cases} x+4y=5-3y \\ 2x+3y=6 \end{cases}

Video Solution

Step-by-Step Solution

To solve the given system of equations using the substitution method, follow these steps:

  • Step A: Simplify and solve the first equation for x x .
    Given: x+4y=53y x + 4y = 5 - 3y
    Combine like terms: x+4y+3y=5 x + 4y + 3y = 5 x+7y=5 x + 7y = 5
    Now solve for x x : x=57y x = 5 - 7y

  • Step B: Substitute this expression for x x in the second equation: 2x+3y=6 2x + 3y = 6
    Substitute x=57y x = 5 - 7y : 2(57y)+3y=6 2(5 - 7y) + 3y = 6
    Expand and simplify: 1014y+3y=6 10 - 14y + 3y = 6 1011y=6 10 - 11y = 6 11y=610 -11y = 6 - 10 11y=4 -11y = -4
    Solving for y y : y=411=411 y = \frac{-4}{-11} = \frac{4}{11}

  • Step C: Substitute y=411 y = \frac{4}{11} back into the equation for x x : x=57(411) x = 5 - 7(\frac{4}{11}) x=52811 x = 5 - \frac{28}{11}
    Convert 5 to an equivalent fraction: x=55112811 x = \frac{55}{11} - \frac{28}{11} x=2711 x = \frac{27}{11}

The solution to the system of equations is x=2711 x = \frac{27}{11} and y=411 y = \frac{4}{11} .

Answer

x=2711,y=411 x=\frac{27}{11},y=\frac{4}{11}

Exercise #11

Choose the correct answer for the following exercise:

{2x+3y=144x+6y=28 \begin{cases} -2x+3y=14 \\ -4x+6y=28 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system of equations, follow these steps:

  • Step 1: Simplify the second equation:
    The second equation is 4x+6y=28-4x + 6y = 28. By dividing every term by 2, we get:
    2x+3y=14-2x + 3y = 14.
  • Step 2: Compare the simplified second equation to the first equation:
    Both equations are now 2x+3y=14-2x + 3y = 14.

Since both equations are identical after simplification, this indicates that the system represents the same line.

Therefore, the system has infinite solutions because any point that satisfies one equation will satisfy the other.

Thus, the correct answer is Infinite solutions.

Answer

Infinite solutions

Exercise #12

Choose the correct answer for the following exercise:

{8x+5y=1024x+15y=30 \begin{cases} -8x+5y=10 \\ -24x+15y=30 \end{cases}

Video Solution

Step-by-Step Solution

To solve this problem using the substitution method, we'll carefully examine the structure of the given system of equations:

  • Given equations:
    1) 8x+5y=10 -8x + 5y = 10
    2) 24x+15y=30 -24x + 15y = 30

Notice that the second equation is exactly three times the first equation:

24x+15y=3(8x+5y)=3×10=30 -24x + 15y = 3(-8x + 5y) = 3 \times 10 = 30

This implies the two equations are not independent; rather, they are multiples of each other.

This insight tells us that every solution of the first equation is also a solution of the second equation, which means:

The system has infinitely many solutions.

Given this conclusion, when examining the choices provided, the correct choice is "Infinite solutions."

Therefore, the solution to the system of equations is that it has infinite solutions.

Answer

Infinite solutions

Exercise #13

Look at the two equations below. Calculate the values of x and y using the substitution method.

{xy2+y+x3=6yx5y+x1=8 \begin{cases}\frac{x-y}{2}+\frac{-y+x}{3}=-6 \\ \frac{-y-x}{5}-\frac{y+x}{1}=8\end{cases}

Video Solution

Step-by-Step Solution

To solve this problem, we'll break it down into clear steps:

  • Step 1: Simplify the given equations for easier manipulation.
  • Step 2: Use the substitution method to express one variable in terms of the other from one equation.
  • Step 3: Insert this expression into the other equation to solve for one variable.
  • Step 4: Finally, substitute back to find the second variable.

Now, let's work through each step:

Step 1: Simplify the first equation.
The first equation is: xy2+y+x3=6 \frac{x-y}{2} + \frac{-y+x}{3} = -6
First, let's find a common denominator of 6 for the fractions: 3(xy)+2(y+x)6=6 \frac{3(x-y) + 2(-y+x)}{6} = -6
This simplifies to: 3x3y2y+2x6=6 \frac{3x-3y-2y+2x}{6} = -6
5x5y6=6 \frac{5x-5y}{6} = -6

Step 1 (cont.): Multiply both sides by 6 to get rid of the denominator:
5x5y=36 5x - 5y = -36
Divide every term by 5 to make it simpler: xy=365 x - y = -\frac{36}{5} x=y365 x = y - \frac{36}{5} (Equation 1)

Step 2: Simplify the second equation.
The second equation is: yx5(y+x)=8 \frac{-y-x}{5} - (y + x) = 8 Multiply through by 5 to clear the fraction from the first term: yx5(y+x)=40 -y-x - 5(y + x) = 40 This expands to: yx5y5x=40 -y-x - 5y - 5x = 40 Combine like terms: 6y6x=40 -6y - 6x = 40 Divide every term by -6 for simplicity: y+x=406 y + x = -\frac{40}{6} y+x=203 y + x = -\frac{20}{3} (Equation 2)

Step 3: Substitute for x x in Equation 2 using Equation 1.
From (Equation 1), x=y365 x = y - \frac{36}{5} . Substitute this into Equation 2: y+(y365)=203 y + (y - \frac{36}{5}) = -\frac{20}{3} This gives: 2y365=203 2y - \frac{36}{5} = -\frac{20}{3} Add 365\frac{36}{5} to both sides to isolate 2y2y: 2y=203+365 2y = -\frac{20}{3} + \frac{36}{5}

Convert both terms to a common denominator to add them together. The common denominator of 3 and 5 is 15: 2y=10015+10815 2y = -\frac{100}{15} + \frac{108}{15} This simplifies to: 2y=815 2y = \frac{8}{15} Divide both sides by 2 to solve for y y : y=4150.266 y = \frac{4}{15} \approx 0.266

Step 4: Solve for x x using y y 's value in Equation 1.
Plug y=415 y = \frac{4}{15} back into Equation 1: x=415365 x = \frac{4}{15} - \frac{36}{5} To add, convert to a common denominator, which can be 15: x=41510815 x = \frac{4}{15} - \frac{108}{15} x=410815 x = \frac{4 - 108}{15} x=104156.933 x = -\frac{104}{15} \approx -6.933

Therefore, after solving both variables, the values that satisfy the given system of equations are:
x6.933, y0.266 x \approx -6.933,\ y \approx 0.266 .

Answer

x=6.933,y=0.266 x=-6.933,y=0.266

Exercise #14

Solve the following equations for x and y using the substitution method:

{2xy2+3y+x5=7yx85y+x6=4 \begin{cases} \frac{2x-y}{2}+\frac{-3y+x}{5}=7 \\ \frac{-y-x}{8}-\frac{5y+x}{6}=4 \end{cases}

Video Solution

Step-by-Step Solution

To solve the system of equations using substitution:

Step 1: Simplify each equation.

First equation:

2xy2+3y+x5=7\frac{2x - y}{2} + \frac{-3y + x}{5} = 7

Multiply by 10 to eliminate denominators:

(2xy)×5+(3y+x)×2=70(2x - y) \times 5 + (-3y + x) \times 2 = 70 10x5y6y+2x=7010x - 5y - 6y + 2x = 70 12x11y=70(1)12x - 11y = 70\quad\text{(1)}

Second equation:

yx85y+x6=4\frac{-y - x}{8} - \frac{5y + x}{6} = 4

Multiply by 24 to eliminate denominators:

(yx)×3(5y+x)×4=96( -y - x) \times 3 - (5y + x) \times 4 = 96 3y3x20y4x=96-3y - 3x - 20y - 4x = 96 7x23y=96(2)-7x - 23y = 96\quad\text{(2)}

Step 2: Solve the first equation for xx:

12x=70+11y12x = 70 + 11y x=70+11y12(3)x = \frac{70 + 11y}{12}\quad\text{(3)}

Step 3: Substitute Equation (3) into Equation (2):

7(70+11y12)23y=96-7\left(\frac{70 + 11y}{12}\right) - 23y = 96

Clear while multiplying by 12:

7(70+11y)276y=1152-7(70 + 11y) - 276y = 1152 49077y276y=1152-490 - 77y - 276y = 1152 353y=1642-353y = 1642 y=4.65y = -4.65

Step 4: Substitute y=4.65y = -4.65 back into Equation (3) to find xx:

x=70+11(4.65)12x = \frac{70 + 11(-4.65)}{12} x=7051.1512x = \frac{70 - 51.15}{12} x=18.8512x = \frac{18.85}{12} x=1.57x = 1.57

Therefore, the solution to the problem is x=1.57 x = 1.57 , y=4.65 y = -4.65 .

Answer

x=1.57,y=4.65 x=1.57,y=-4.65

Exercise #15

Choose the correct answer for the following exercise:

{3x4y=109x12y=15 \begin{cases} 3x-4y=10 \\ 9x-12y=15 \end{cases}

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Verify if both equations in the system are proportional.
  • Step 2: Determine if they result in a true or false statement when simplified.
  • Step 3: Conclude about the solution set based on the results.

Now, let's work through each step:
Step 1: Start with the system of equations:
{3x4y=109x12y=15\begin{cases} 3x - 4y = 10 \\ 9x - 12y = 15 \end{cases}

Step 2: Check if the second equation is a multiple of the first equation.
Divide each coefficient of the second equation by 3:
- (9x)÷3=3x(9x) \div 3 = 3x
- (12y)÷3=4y(-12y) \div 3 = -4y
- (15)÷3=5(15) \div 3 = 5
Thus, converting: {3x4y=103x4y=5\begin{cases} 3x - 4y = 10 \\ 3x - 4y = 5 \end{cases}

Step 3: We notice that while the left sides of both equations are identical, the right sides differ:
This results in a logical contradiction because 10510 \neq 5.
Thus, these lines are parallel and distinct, indicating that the system has no common points of intersection, hence no solution.

Therefore, the correct conclusion for this system of equations is No solution.

Answer

No solution

Exercise #16

Solve the following equations for x and y using the substitution method:

{2x3y4+xy5=302y+x83yx4=12 \begin{cases} \frac{2x-3y}{4}+\frac{x-y}{5}=30 \\ \frac{2y+x}{8}-\frac{3y-x}{4}=12 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system, we'll first simplify and manipulate the equations to perform substitution. Let's begin:

The first equation is 2x3y4+xy5=30 \frac{2x-3y}{4} + \frac{x-y}{5} = 30 .
To eliminate the fractions, multiply through by 20 (the least common multiple of 4 and 5):

20(2x3y4)+20(xy5)=20×30 20 \left( \frac{2x-3y}{4} \right) + 20 \left( \frac{x-y}{5} \right) = 20 \times 30

Simplifying each term gives:
5(2x3y)+4(xy)=600 5(2x - 3y) + 4(x - y) = 600

Expanding the terms:

10x15y+4x4y=600 10x - 15y + 4x - 4y = 600

Combine like terms:

14x19y=600 14x - 19y = 600     [Equation (1)]

Next, let's work on the second equation: 2y+x83yx4=12 \frac{2y + x}{8} - \frac{3y - x}{4} = 12 .
Multiply through by 8 to clear the denominators:

8(2y+x8)8(3yx4)=8×12 8 \left( \frac{2y + x}{8} \right) - 8 \left( \frac{3y - x}{4} \right) = 8 \times 12

Simplifying each term gives:

2y+x2(3yx)=96 2y + x - 2(3y - x) = 96

Expanding the terms:

2y+x6y+2x=96 2y + x - 6y + 2x = 96

Combine like terms for a simplified second equation:

3x4y=96 3x - 4y = 96     [Equation (2)]

Now let's use substitution:

From Equation (2), solve for x x :

3x=4y+96 3x = 4y + 96

x=4y+963 x = \frac{4y + 96}{3}

Substitute this expression for x x in Equation (1):

14(4y+963)19y=600 14\left( \frac{4y + 96}{3} \right) - 19y = 600

Multiply through by 3 to clear the fraction:

14(4y+96)57y=1800 14(4y + 96) - 57y = 1800

56y+134457y=1800 56y + 1344 - 57y = 1800

Combine like terms:

y+1344=1800 -y + 1344 = 1800

Solve for y y :

y=18001344=456 -y = 1800 - 1344 = 456

y=456 y = -456

Substitute y=456 y = -456 back into the expression for x x :

x=4(456)+963 x = \frac{4(-456) + 96}{3}

x=1824+963 x = \frac{-1824 + 96}{3}

x=17283 x = \frac{-1728}{3}

x=576 x = -576

Thus, the solution for the system is:

x=576,y=456 x = -576, y = -456

After verifying against the provided answer choices, the solution is consistent with choice 4.

Therefore, the solution to the problem is x=576,y=456 x = -576, y = -456 .

Answer

x=576,y=456 x=-576,y=-456

Exercise #17

Choose the correct answer for the following exercise:

{8x+5y=216x+10y=5 \begin{cases} -8x+5y=2 \\ -16x+10y=5 \end{cases}

Video Solution

Step-by-Step Solution

To solve this system of equations, we'll follow these steps:

  • Step 1: Analyze the proportions of the coefficients to check for potential parallelism or redundancy.
  • Step 2: Attempt elimination to directly identify any inconsistencies.

Now, let's perform the analysis:
Step 1: Notice the proportionality in both equations:
The first equation is 8x+5y=2-8x + 5y = 2 and the second is 16x+10y=5-16x + 10y = 5. Multiply the first equation by 2:
16x+10y=4-16x + 10y = 4.
This equation is now equivalent in terms of xx and yy to the second equation, but with a different constant term.

Step 2: Subtract the modified first equation from the second equation:

(16x+10y)(16x+10y)=54 (-16x + 10y) - (-16x + 10y) = 5 - 4 0=1 0 = 1

This result, 0=10 = 1, is a contradiction, indicating that the system is inconsistent.

Therefore, the system of equations has no solution.

Answer

No solution

Exercise #18

Solve the following equations for x and y using the substitution method.

{3x2y8+xy2=144x+3y52x2y3=20 \begin{cases} \frac{3x-2y}{8}+\frac{x-y}{2}=14 \\ \frac{4x+3y}{5}-\frac{2x-2y}{3}=20 \end{cases}

Video Solution

Step-by-Step Solution

To solve the given system of equations using substitution, follow these steps:

First, we simplify the given equations. Let's start with the first equation:

3x2y8+xy2=14. \frac{3x-2y}{8} + \frac{x-y}{2} = 14.

Find a common denominator for fractions on the left side. The common denominator of 8 and 2 is 8:

3x2y8+4(xy)8=143x2y+4x4y8=14. \frac{3x-2y}{8} + \frac{4(x-y)}{8} = 14 \rightarrow \frac{3x-2y+4x-4y}{8} = 14.

Simplify inside the fraction:

7x6y8=147x6y=112.(multiply through by 8) \frac{7x-6y}{8} = 14 \rightarrow 7x - 6y = 112. \quad \text{(multiply through by 8)}

This is our simplified form for the first equation.

Now, simplify the second equation:

4x+3y52x2y3=20. \frac{4x+3y}{5} - \frac{2x-2y}{3} = 20.

Find a common denominator for the fractions, which is 15:

3(4x+3y)5(2x2y)15=20. \frac{3(4x + 3y) - 5(2x - 2y)}{15} = 20.

Distribute and simplify:

12x+9y10x+10y15=202x+19y15=20. \frac{12x + 9y - 10x + 10y}{15} = 20 \rightarrow \frac{2x + 19y}{15} = 20.

Multiply through by 15 to clear the fraction:

2x+19y=300. 2x + 19y = 300.

Now, we have two simplified equations:

{7x6y=1122x+19y=300. \begin{cases} 7x - 6y = 112 \\ 2x + 19y = 300 \end{cases}.

From the first equation, solve for xx:

7x=6y+112x=6y+1127. 7x = 6y + 112 \rightarrow x = \frac{6y + 112}{7}.

Substitute x=6y+1127x = \frac{6y + 112}{7} into the second equation:

2(6y+1127)+19y=300. 2\left(\frac{6y + 112}{7}\right) + 19y = 300.

Distribute:

12y+2247+19y=300. \frac{12y + 224}{7} + 19y = 300.

Clear the fraction by multiplying through by 7:

12y+224+133y=2100. 12y + 224 + 133y = 2100.

Combine like terms:

145y+224=2100. 145y + 224 = 2100.

Subtract 224 from both sides:

145y=1876y=187614512.93. 145y = 1876 \rightarrow y = \frac{1876}{145} \approx 12.93.

Now, substitute y12.93y \approx 12.93 back into x=6y+1127x = \frac{6y + 112}{7}:

x=6(12.93)+1127=77.58+1127=189.58727.08. x = \frac{6(12.93) + 112}{7} = \frac{77.58 + 112}{7} = \frac{189.58}{7} \approx 27.08.

Therefore, the solution to the system is:

x27.08,y12.93 x \approx 27.08, \, y \approx 12.93 .

This corresponds to choice 1:

x=27.08,y=12.93 x = 27.08, y = 12.93 .

Answer

x=27.08,y=12.93 x=27.08,y=12.93

Exercise #19

Solve the following equations for x and y using the substitution method.

{x+3y6+5xy3=122x4y102x2y5=15 \begin{cases} \frac{-x+3y}{6}+\frac{5x-y}{3}=12 \\ \frac{2x-4y}{10}-\frac{-2x-2y}{5}=15 \end{cases}

Video Solution

Step-by-Step Solution

To solve the system of equations using the substitution method, follow these detailed steps:

We start with the given system:

{x+3y6+5xy3=122x4y102x2y5=15 \begin{cases} \frac{-x+3y}{6}+\frac{5x-y}{3} = 12 \\ \frac{2x-4y}{10}-\frac{-2x-2y}{5} = 15 \end{cases}

Step 1: Clear Fractions

  • For the first equation, multiply through by 6 (the least common multiple of 6 and 3):
  • (x+3y)+2(5xy)=72 (-x + 3y) + 2(5x - y) = 72 x+3y+10x2y=72 -x + 3y + 10x - 2y = 72 9x+y=72(Equation 1) 9x + y = 72 \quad \text{(Equation 1)}
  • For the second equation, multiply through by 10 (the LCM of 10 and 5):
  • 2x4y10×102x2y5×10=150 \frac{2x-4y}{10} \times 10 - \frac{-2x-2y}{5} \times 10 = 150 (2x4y)+(4x4y)=150 (2x - 4y) + (-4x - 4y) = 150 2x4y+4x+4y=150 2x - 4y + 4x + 4y = 150 6x=150 6x = 150 x=25(Equation 2) x = 25 \quad \text{(Equation 2)}

Step 2: Substitute & Solve

Since we have x=25 x = 25 from Equation 2, substitute x=25 x = 25 into Equation 1:

9(25)+y=72 9(25) + y = 72 225+y=72 225 + y = 72 y=72225 y = 72 - 225 y=153 y = -153

Therefore, the solution to the system is x=25,y=153\boxed{x = 25, y = -153}.

Answer

x=25,y=153 x=25,y=-153

Exercise #20

Find the value of x and and band the substitution method.

{x+3y=124x+2y=10 \begin{cases} -x+3y=12 \\ 4x+2y=10 \end{cases}

Video Solution

Answer

x=37,y=297 x=\frac{3}{7},y=\frac{29}{7}