Question

1. Which of the following ordered pairs are solutions to the system of equations below?

4x + 4y = -9
Y = 2x - 13
A : (-3, -7)
B : (3-7)
C : (3,7)
D : (-3,7)

Answer 1

43\ 12 , 35/ 6

Explanation:

43\ 12 , 35/ 6

Answer 2

Answer: B: (3, -7)

Explanation:

4x + 4y = -9

y = 2x - 13

Use Substitution:

4x + 4(2x - 13) = -9

4x + 8x - 52 = -9

12x - 52 = -9

12x = 43

`x=(43)/(12)`

None of the options provided are valid so either there is a typo on your worksheet or you typed in one of the equations wrong.

Plan B: Input the choices into the equation to see which one makes a true statement.

4x + 4y = -9

A) (x, y) = (-3, -7)

4(-3) + 4(-7) = -9

-12 + -28 = -9

-40 ≠ -9

B) (x, y) = (3, -7)

4(3) + 4(-7) = -9

12 + -28 = -9

-16 ≠ -9

C) (x, y) = (3, 7)

4(3) + 4(7) = -9

12 + 28 = -9

40 ≠ -9

D) (x, y) = (-3, 7)

4(-3) + 4(7) = -9

-12 + 28 = -9

16 ≠ -9

Obviously there is something wrong with the first equation because none of the options provide a true statement.

y = 2x - 13

A) (x, y) = (-3, -7)

-7 = 2(-3) - 13

-7 = -6 -13

-7 ≠ -19

B) (x, y) = (3, -7)

-7 = 2(3) - 13

-7 = 6 -13

-7 = -7 this works!!!

C) (x, y) = (3, 7)

7 = 2(3) - 13

7 = 6 -13

7 ≠ -7

D) (x, y) = (-3, 7)

7 = 2(-3) - 13

7 = -6 -13

7 ≠ -19

Option B is the only one that provides a true statement so this must be the answer.