Question

What values of x make the equation true?
-2x² +15= x² - 12

Answer 1

x = ± 3

Explanation:

-2x^2 +15 +12 - x^2 = 0
-3x^2 + 27 = 0
-3x^2 = -27
x^2 = -27/-3
x^2 = 9
x = ± 3

Answer 2

x = - 3 , x = 3

Explanation:

given the equation

- 2x² + 15 = x² - 12 ( subtract x² from both sides )

- 2x² - x² + 15 = x² - x² - 12 ( simplify both sides )

- 3x² + 15 = - 12 ( subtract 15 from both sides )

- 3x² + 15 - 15 = - 12 - 15 ( simplify both sides )

- 3x² = - 27 ( divide both sides by - 3 )

`(-3)/(-3)` x² =
`(-27)/(-3)` , that is

x² = 9 ( take square root of both sides )

`√(x^2)` = ±
`√(9)`

x = ± 3

values of x that make the equation true are x = - 3 and x = 3