Q:

Which of the following are solutions to 2x^2-8x-90? select all that apply.

Accepted Solution

A:
Simplifying:
2x2 + -8x + -90 = 0

Reorder the terms:
-90 + -8x + 2x2 = 0

Solving
-90 + -8x + 2x2 = 0

Solving for variable 'x'.

Factor out the Greatest Common Factor (GCF), '2'.
2(-45 + -4x + x2) = 0

Factor a trinomial.
2((-5 + -1x)(9 + -1x)) = 0

Ignore the factor 2.
Subproblem 1:

Set the factor '(-5 + -1x)' equal to zero and attempt to solve:

Simplifying
-5 + -1x = 0

Solving
-5 + -1x = 0

Move all terms containing x to the left, all other terms to the right.

Add '5' to each side of the equation.
-5 + 5 + -1x = 0 + 5

Combine like terms:
-5 + 5 = 0 0 + -1x = 0 + 5 -1x = 0 + 5

Combine like terms:
0 + 5 = 5 -1x = 5

Divide each side by '-1'.
x = -5

Simplifying
x = -5

Subproblem 2:

Set the factor '(9 + -1x)' equal to zero and attempt to solve:

Simplifying
9 + -1x = 0

Solving
9 + -1x = 0

Move all terms containing x to the left, all other terms to the right.

Add '-9' to each side of the equation.
9 + -9 + -1x = 0 + -9

Combine like terms:
9 + -9 = 0 0 + -1x = 0 + -9 -1x = 0 + -9

Combine like terms:
0 + -9 = -9 -1x = -9

Divide each side by '-1'.
x = 9

Simplifying x = 9

Solution
x = {-5, 9}