Question

Find an equivalent system of equations for the following system: 3x + 3y = 0 −4x + 4y = −8 3x + 3y = 0 7x − y = 8 3x + 3y = 0 −7x − y = 8 3x + 3y = 0 −7x + 7y = 8 3x + 3y = 0 −4x + 7y = 8

Answer 1

Answer:

A.

3x + 3y = 0

7x − y = 8

Step-by-step explanation:

Given

3x + 3y = 0

-4x + 4y = -8

Required

Find the equivalent

To solve for the equivalent we simply solve for x and y in the given equation.

Subtract 3x from both sides in 3x + 3y = 0

3x - 3x + 3y = 0 - 3x

3y = -3x

Multiply both sides by ⅓

⅓ * 3y = -3x * ⅓

y = -x

Substitute -x for y in -4x + 4y = -8

-4x + 4(-x) = -8

-4x -4x = -8

-8x = -8

Multiply both sides by -⅛

-⅛ * -8x = -⅛ * -8

x = 1

Recall that y = -x

y = -1

So, we have that x = 1 and y = -1

We'll substitute these values in the list of options;

A.

3x + 3y = 0

7x − y = 8

7(1) - -(1) = 8

7 + 1 = 8 ----- This is equivalent

B.

3x + 3y = 0

−7x − y = 8

-7(1) - (-1) = 8

-7 + 1 = 8

-6 ≠ 8 .... This is not an equivalent expression

C.

3x + 3y = 0

−7x + 7y = 8

-7(1) + 7(-1) = 8

-7 -7 = 8

-14 ≠ 8 .... This is also not an equivalent expression

D.

3x + 3y = 0

-4x + 7y = 8

-4(1) + 7(-1) = 8

-4 -7 = 8

-11 ≠ 8 -_- This is also not an equivalent expression