u^2+u-90=0

Solution for u^2+u-90=0 equation:

Simplifying
u2 + u + -90 = 0

Reorder the terms:
-90 + u + u2 = 0

Solving
-90 + u + u2 = 0

Solving for variable 'u'.

Factor a trinomial.
(-10 + -1u)(9 + -1u) = 0

Subproblem 1
Set the factor '(-10 + -1u)' equal to zero and attempt to solve:

Simplifying
-10 + -1u = 0

Solving
-10 + -1u = 0

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

Add '10' to each side of the equation.
-10 + 10 + -1u = 0 + 10

Combine like terms: -10 + 10 = 0
0 + -1u = 0 + 10
-1u = 0 + 10

Combine like terms: 0 + 10 = 10
-1u = 10

Divide each side by '-1'.
u = -10

Simplifying
u = -10
Subproblem 2
Set the factor '(9 + -1u)' equal to zero and attempt to solve:

Simplifying
9 + -1u = 0

Solving
9 + -1u = 0

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

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

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

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

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

Simplifying
u = 9
Solution
u = {-10, 9}