Question
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A. Use Substitution to solve \( x \) and \( y \) : 1. \( x+2 y=5 \) and \( 4 x+2 y=-10 \) 2. \( 2 x-4 y=10 \) and \( 3 x+5 y=-29 \) 3. \( 2 x-3 y=4 \) and \( 4 x-3 y=20 \)

Ask by Boyd Medina. in South Africa
Mar 09,2025

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Tutor-Verified Answer

Answer

1. \( x = -5 \), \( y = 5 \) 2. \( x = -3 \), \( y = -4 \) 3. \( x = 8 \), \( y = 4 \)

Solution

1. Given the system \[ x + 2y = 5, \] \[ 4x + 2y = -10. \] Solve the first equation for \( x \): \[ x = 5 - 2y. \] Substitute \( x = 5 - 2y \) into the second equation: \[ 4(5 - 2y) + 2y = -10. \] Simplify: \[ 20 - 8y + 2y = -10, \] \[ 20 - 6y = -10. \] Subtract 20 from both sides: \[ -6y = -30. \] Divide by \(-6\): \[ y = 5. \] Substitute \( y = 5 \) back into \( x = 5 - 2y \): \[ x = 5 - 2(5) = 5 - 10 = -5. \] **Solution for the first system:** \( x = -5 \), \( y = 5 \). 2. Given the system \[ 2x - 4y = 10, \] \[ 3x + 5y = -29. \] Solve the first equation for \( x \): \[ x = \frac{10 + 4y}{2} = 5 + 2y. \] Substitute \( x = 5 + 2y \) into the second equation: \[ 3(5 + 2y) + 5y = -29. \] Simplify: \[ 15 + 6y + 5y = -29, \] \[ 15 + 11y = -29. \] Subtract 15 from both sides: \[ 11y = -44. \] Divide by 11: \[ y = -4. \] Substitute \( y = -4 \) back into \( x = 5 + 2y \): \[ x = 5 + 2(-4) = 5 - 8 = -3. \] **Solution for the second system:** \( x = -3 \), \( y = -4 \). 3. Given the system \[ 2x - 3y = 4, \] \[ 4x - 3y = 20. \] Notice that both equations have the term \(-3y\). Subtract the first equation from the second to eliminate \(y\): \[ (4x - 3y) - (2x - 3y) = 20 - 4. \] Simplify: \[ 4x - 3y - 2x + 3y = 16, \] \[ 2x = 16. \] Divide by 2: \[ x = 8. \] Substitute \( x = 8 \) into the first equation: \[ 2(8) - 3y = 4, \] \[ 16 - 3y = 4. \] Subtract 16 from both sides: \[ -3y = 4 - 16 = -12. \] Divide by \(-3\): \[ y = 4. \] **Solution for the third system:** \( x = 8 \), \( y = 4 \).

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The Deep Dive

To solve these systems of equations using substitution, let’s first isolate one variable in one equation and substitute it into the other. 1. From the first equation \( x + 2y = 5 \), we can isolate \( x \): \[ x = 5 - 2y \] Substitute this expression for \( x \) in the second equation \( 4x + 2y = -10 \): \[ 4(5 - 2y) + 2y = -10 \] Simplifying this gives: \[ 20 - 8y + 2y = -10 \implies -6y = -30 \implies y = 5 \] Now substitute \( y = 5 \) back into \( x = 5 - 2y \): \[ x = 5 - 2(5) = -5 \] So, the solution is \( x = -5 \), \( y = 5 \). 2. In the second system, starting with \( 2x - 4y = 10 \), we can isolate \( x \): \[ 2x = 10 + 4y \implies x = 5 + 2y \] Substitute this into the second equation \( 3x + 5y = -29 \): \[ 3(5 + 2y) + 5y = -29 \] Simplifying gives: \[ 15 + 6y + 5y = -29 \implies 11y = -44 \implies y = -4 \] Now substituting \( y = -4 \) back into \( x = 5 + 2y \): \[ x = 5 + 2(-4) = 5 - 8 = -3 \] So, the solution is \( x = -3 \), \( y = -4 \). 3. For the third system starting from \( 2x - 3y = 4 \), isolate \( x \): \[ 2x = 4 + 3y \implies x = 2 + \frac{3}{2}y \] Substitute this into the second equation \( 4x - 3y = 20 \): \[ 4(2 + \frac{3}{2}y) - 3y = 20 \] Simplifying gives: \[ 8 + 6y - 3y = 20 \implies 3y = 12 \implies y = 4 \] Now substitute \( y = 4 \) back: \[ x = 2 + \frac{3}{2}(4) = 2 + 6 = 8 \] So, the solution is \( x = 8 \), \( y = 4 \). Final Solutions: 1. \( (x, y) = (-5, 5) \) 2. \( (x, y) = (-3, -4) \) 3. \( (x, y) = (8, 4) \)

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