Solve the equation 2x² + 2x + 12 = 3x² – x + 2.
a. x = –5, x = –2
b. x = 2, x = –5
c. x = 2, x = 5
d. x = –2, x = 5

D: x = -2, x = 5

Step-by-step explanation:

To solve for a variable, you first have to isolate it on one side of the equation. Remember that whatever you do to one side, you also have to do to the other.

2x² + 2x + 12 = 3x² - x + 2   Subtract 2x² from both sides

2x + 12 = x² - x + 2   Subtract 2x from both sides

12 = x² - 3x + 2   Subtract 12 from both sides

0 = x² - 3x - 10   Using factoring, split this into two expressions

0 = (x - 5) (x + 2)   Set each expression equal to 0

x - 5 = 0 and x + 2 = 0   Solve each expression

x = 5 and x = -2

Now, you can plug in both answers to check your work

2x² + 2x + 12 = 3x² - x + 2   Plug in 5

2(5)² + 2(5) + 12 = 3(5)² - 5 + 2   Simplify

2(25) + 10 + 12 = 3(25) - 5 + 2   Simplify some more

50 + 10 + 12 = 75 - 5 + 2   Simplify one more time

72 = 72   It works!

2x² + 2x + 12 = 3x² - x + 2   Plug in -2

2(-2)² +2(-2) + 12 = 3(-2)² -(-2) + 2   Simplify

2(4) - 4 + 12 = 3(4) + 2 + 2   Simplify again

8 - 4 + 12 = 12 + 2 + 2   Simplify one more time

16 = 16   It also works!