Question

Which values of x make this equation true?

x^2+8x=-15

Answer 1

Answer: x = -5, -3

Explanation:

This is a quadratic function. First, we will move all terms to one side.

x² + 8x = -15

x² + 8x + 15 = 0

Next, we see that we cannot easily factor this equation. For this problem, we will use the quadratic formula. a = 1, b = 8, and c =15.

`\displaystyle x=(-b\pm√(b^2-4ac) )/(2a)`

`\displaystyle x=(-8\pm√(8^2-4(1)(15)) )/(2(1))`

`\displaystyle x=(-8\pm√(64-60) )/(2)`

`\displaystyle x=(-8\pm√(4) )/(2)`

`\displaystyle x=(-8-2 )/(2)`,
`\displaystyle x=(-8+2 )/(2)`

x = -5, -3

We can also check our answer by substituting.

x² + 8x = -15 ➜ (-3)² + 8(-3) = -15 ✓

x² + 8x = -15 ➜ (-5)² + 8(-5) = -15 ✓

I know this is not one of your given answer options, but this is the solution to the given quadratic function. Was the question copied down correctly?