Question
11. Use the elimination method by subtraction to solve for \( x \) and then \( y \). Equation \( 1 \quad 4 x-7 y=18 \) Equation \( 2 \quad-3 x-7 y=-38 \) 11a First solve for \( x \) ( \( x=8 \) 11b Now solve for \( y \) Enter your next step here
Ask by Todd Davies. in the United States
Mar 08,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
\( x = 8 \) and \( y = 2 \).
Solution
Solve the system of equations \( 4x-7y=18;-3x-7y=-38 \).
Solve the system of equations by following steps:
- step0: Solve using the substitution method:
\(\left\{ \begin{array}{l}4x-7y=18\\-3x-7y=-38\end{array}\right.\)
- step1: Solve the equation:
\(\left\{ \begin{array}{l}x=\frac{18+7y}{4}\\-3x-7y=-38\end{array}\right.\)
- step2: Substitute the value of \(x:\)
\(-3\times \frac{18+7y}{4}-7y=-38\)
- step3: Simplify:
\(-\frac{3\left(18+7y\right)}{4}-7y=-38\)
- step4: Multiply both sides of the equation by LCD:
\(\left(-\frac{3\left(18+7y\right)}{4}-7y\right)\times 4=-38\times 4\)
- step5: Simplify the equation:
\(-54-49y=-152\)
- step6: Move the constant to the right side:
\(-49y=-152+54\)
- step7: Add the numbers:
\(-49y=-98\)
- step8: Change the signs:
\(49y=98\)
- step9: Divide both sides:
\(\frac{49y}{49}=\frac{98}{49}\)
- step10: Divide the numbers:
\(y=2\)
- step11: Substitute the value of \(y:\)
\(x=\frac{18+7\times 2}{4}\)
- step12: Calculate:
\(x=8\)
- step13: Calculate:
\(\left\{ \begin{array}{l}x=8\\y=2\end{array}\right.\)
- step14: Check the solution:
\(\left\{ \begin{array}{l}x=8\\y=2\end{array}\right.\)
- step15: Rewrite:
\(\left(x,y\right) = \left(8,2\right)\)
The solution to the system of equations is \( x = 8 \) and \( y = 2 \).
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Extra Insights
To solve for \( y \), we can substitute \( x = 8 \) back into either of the original equations. Let's use Equation 1: \[ 4(8) - 7y = 18 \] This simplifies to: \[ 32 - 7y = 18 \] Now, rearranging gives: \[ -7y = 18 - 32 \] \[ -7y = -14 \] Dividing both sides by -7 gives: \[ y = 2 \] So, the solutions are \( x = 8 \) and \( y = 2 \)!