25 + x^2 + 10x = 0

solve for x

Answer is -5

Simplifying
25 + x2 + 10x = 0

Reorder the terms:
25 + 10x + x2 = 0

Solving
25 + 10x + x2 = 0

Solving for variable 'x'.

Factor a trinomial.
(5 + x)(5 + x) = 0

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

Simplifying
5 + x = 0

Solving
5 + x = 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 + x = 0 + -5

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

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