Detailed Equation Analysis: Decipher the System -2x+3y=4, x-4y=8

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

{2x+3y=4x4y=8 \begin{cases} -2x+3y=4 \\ x-4y=8 \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
00:03 Isolate X
00:10 This is the expression of X using Y
00:17 Substitute this expression to find Y
00:30 Open parentheses properly, multiply by each factor
00:41 Isolate Y
00:48 Collect terms
01:01 Isolate Y
01:08 This is the value of Y
01:13 This is the value of Y
01:36 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

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

{2x+3y=4x4y=8 \begin{cases} -2x+3y=4 \\ x-4y=8 \end{cases}

2

Step-by-step solution

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

  • First, look at our system of equations:
    • Equation 1: 2x+3y=4-2x + 3y = 4
    • Equation 2: x4y=8x - 4y = 8
  • We choose to use the elimination method to remove one variable from the equations. We'll aim to eliminate xx.
  • To achieve this, multiply the second equation by 2 so that we can align the coefficients of xx in both equations:
    • New Equation 2: 2x8y=162x - 8y = 16
  • Now, add the transformed second equation to Equation 1 to cancel out xx:
  • (2x+3y)+(2x8y)=4+16 (-2x + 3y) + (2x - 8y) = 4 + 16
  • This simplifies to:
  • 5y=20 -5y = 20
  • Solve for yy:
  • y=4 y = -4
  • With yy known, substitute back into the second original equation to determine xx:
  • x4(4)=8 x - 4(-4) = 8
  • Simplify and solve for xx:
  • x+16=8x=816x=8 x + 16 = 8 \quad \Rightarrow \quad x = 8 - 16 \quad \Rightarrow \quad x = -8

We have now found the solution for the system of equations. The values are x=8x = -8 and y=4y = -4.

Thus, the correct answer choice is x=8,y=4 x = -8, y = -4 .

3

Final Answer

x=8,y=4 x=-8,y=-4

Practice Quiz

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Solve the following equations:

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

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