Question

Solve the system using elimination
3x + 3y = –9
3x – 3y = 21
a. (3, –6) b. (–5, 2) c. (3, 3) d. (2, –5)

Answer 1

The answer is d. (2,-5)

Answer 2

The y's cancel out leaving you with \[6x = 12\] Divide by 6 and x=2.. Plug in x =2 into any of the equations \[3(2) + 3y = -9\] Evaluate and solve for y \[6 + 3y = -9\] \[3y = -15\] \[y = -5\] Thus the answer is d.

Answer 3

3x + 3y = -9
3x - 3y = 21
______________ Just add them,
6x + 0y = 12
6x = 12
x = 2
Now that you have x, which is 2, plug 2 back in one of the equations.

3(2) + 3y = -9
6 + 3y = -9
-6 -6 Subtract six from both sides.
3y = -15
y = -5
Now you have both x and y, just write them both as coordinates, (2,-5)