Answer:
x = ±

Explanation:
-8 - 8x^2= -31
Since this is a quadratic, it needs to be factored.
First, move the x to the other side:
-8 = 8x^2 - 31
Then, get the x alone by first adding 31:
23 = 8x^2
then dividing by 8:
x^2 = 23/8
Finally, square root both sides and remember the even roots property:
x = ±

and simplify the root 8:
x = ±

Note: This answer may have a mistake.