Question

If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to y from the second equation is substituted into the first equation.

2x – 7y = 4
3x + y = –17

Answer 1

expression of y from second equation:
3x + y = -17
y = -17 - 3x       (1)

Now we substitute this y in first equation:
2x - 7(-17 - 3x) = 4
2x + 119 + 21x = 4
23x = -115
x = -5

now we express value of x in equation (1)
y = -17 - 3*(-5) = -2 

Answer 2

Answer:

D: 2x-7(-3x-17)=4

Step-by-step explanation:

1) Solve for y

3x+y=-17

Subtract 3x from both sides to isolate y

y=-3x-17

2) Substitute into the first equation (2x-7y=4)

We solved for y, so replace y with -3x-17

2x-7(-3x-17)=4 !