Solve for X and Y Using Substitution: System of Equations with x + y = 5 and 2x - 3y = -15

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}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve the system of equations
00:07 Isolate X
00:17 This is the expression for X, substitute in the second equation to find Y
00:41 Properly expand brackets, multiply by each factor
00:51 Isolate Y
01:05 Collect like terms
01:22 This is the value of Y
01:29 Now substitute the value of Y to find X
01:45 And this is the solution to the problem

Step-by-step written solution

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1

Understand the problem

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}

2

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+3x=155x15=155x=0x=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.
y=50y=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

3

Final Answer

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

Practice Quiz

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Solve the following equations:

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

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