100=X(X+15X)

Solution for 100=X(X+15X) equation:

Simplifying
100 = X(X + 15X)

Combine like terms: X + 15X = 16X
100 = X(16X)

Remove parenthesis around (16X)
100 = X * 16X

Reorder the terms for easier multiplication:
100 = 16X * X

Multiply X * X
100 = 16X2

Solving
100 = 16X2

Solving for variable 'X'.

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

Add '-16X2' to each side of the equation.
100 + -16X2 = 16X2 + -16X2

Combine like terms: 16X2 + -16X2 = 0
100 + -16X2 = 0

Add '-100' to each side of the equation.
100 + -100 + -16X2 = 0 + -100

Combine like terms: 100 + -100 = 0
0 + -16X2 = 0 + -100
-16X2 = 0 + -100

Combine like terms: 0 + -100 = -100
-16X2 = -100

Divide each side by '-16'.
X2 = 6.25

Simplifying
X2 = 6.25

Take the square root of each side:
X = {-2.5, 2.5}