Solve the System: Tackling -y + 2/5x = 13 and 1/2y + 2x = 10

Linear Systems with Fractional Coefficients

Solve the above set of equations and choose the correct answer.

{y+25x=1312y+2x=10 \begin{cases} -y+\frac{2}{5}x=13 \\ \frac{1}{2}y+2x=10 \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
00:08 Multiply by 5 to eliminate the fraction
00:22 Now this is the system of equations
00:29 Subtract between the equations
00:47 Collect like terms
00:59 Isolate Y
01:11 This is the value of Y
01:18 Substitute Y value to find X value
01:34 Isolate X
01:43 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the above set of equations and choose the correct answer.

{y+25x=1312y+2x=10 \begin{cases} -y+\frac{2}{5}x=13 \\ \frac{1}{2}y+2x=10 \end{cases}

2

Step-by-step solution

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

Given equations:

  • Equation 1: y+25x=13 -y + \frac{2}{5}x = 13
  • Equation 2: 12y+2x=10 \frac{1}{2}y + 2x = 10

Step 1: Clear fractions in Equation 1 by multiplying through by 5:

5y+2x=65-5y + 2x = 65 ...(Equation 3)

Step 2: Clear fractions in Equation 2 by multiplying through by 2:

y+4x=20y + 4x = 20 ...(Equation 4)

Step 3: Align the coefficients of yy for elimination. Use Equation 3 and Equation 4, where coefficients of yy can be easily handled.

Using Equations 3 and 4:

5y+2x=65-5y + 2x = 65

y+4x=20y + 4x = 20

Step 4: Let's multiply Equation 4 by 5 to align coefficients of yy:

5y+20x=1005y + 20x = 100

Step 5: Add the resulting Equation 4 to Equation 3:

5y+2x+5y+20x=65+100-5y + 2x + 5y + 20x = 65 + 100

22x=16522x = 165

Step 6: Solve for xx:

x=16522=7.5x = \frac{165}{22} = 7.5

Step 7: Substitute x=7.5x = 7.5 back into Equation 4 to solve for yy:

y+4(7.5)=20y + 4(7.5) = 20

y+30=20y + 30 = 20

y=2030=10y = 20 - 30 = -10

Therefore, the solution is x=7.5 and y=10 x = 7.5 \text{ and } y = -10 .

The correct choice from the answer options is:

x=7.5,y=10 x=7.5,y=-10

.

3

Final Answer

x=7.5,y=10 x=7.5,y=-10

Key Points to Remember

Essential concepts to master this topic
  • Clear Fractions: Multiply each equation by LCD to eliminate denominators
  • Elimination Method: Multiply equation 2 by 5: 5y+20x=100 5y + 20x = 100
  • Check Solution: Substitute x=7.5,y=10 x=7.5, y=-10 into both original equations ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to multiply all terms when clearing fractions
    Don't just multiply the fraction terms and leave constants unchanged = unbalanced equation! This creates wrong coefficients and leads to incorrect solutions. Always multiply every single term in the equation by the same number.

Practice Quiz

Test your knowledge with interactive questions

Solve the following equations:

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

FAQ

Everything you need to know about this question

Why should I clear fractions first instead of working with them directly?

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Clearing fractions makes calculations much easier and reduces errors! Working with whole numbers in 5y+2x=65 -5y + 2x = 65 is simpler than y+25x=13 -y + \frac{2}{5}x = 13 .

How do I know which method to use - substitution or elimination?

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For this system, elimination works better because after clearing fractions, the coefficients align nicely. Look for patterns that make one variable easy to eliminate!

What if I get a decimal answer like x = 7.5?

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Decimal answers are completely normal in linear systems! Just make sure to use the exact decimal value when substituting back to check your work.

How can I check if my solution is correct?

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Substitute both values into both original equations. For our answer: (10)+25(7.5)=10+3=13 -(-10) + \frac{2}{5}(7.5) = 10 + 3 = 13 ✓ and 12(10)+2(7.5)=5+15=10 \frac{1}{2}(-10) + 2(7.5) = -5 + 15 = 10 ✓

Why did we multiply the second equation by 5 in the elimination step?

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We needed the y-coefficients to be opposites for elimination. Since equation 3 had 5y -5y and equation 4 had y y , multiplying by 5 gave us +5y +5y to cancel out!

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