19.15=0.9x*x

Solution for 19.15=0.9x*x equation:

Simplifying
19.15 = 0.9x * x

Multiply x * x
19.15 = 0.9x2

Solving
19.15 = 0.9x2

Solving for variable 'x'.

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

Add '-0.9x2' to each side of the equation.
19.15 + -0.9x2 = 0.9x2 + -0.9x2

Combine like terms: 0.9x2 + -0.9x2 = 0.0
19.15 + -0.9x2 = 0.0

Add '-19.15' to each side of the equation.
19.15 + -19.15 + -0.9x2 = 0.0 + -19.15

Combine like terms: 19.15 + -19.15 = 0.00
0.00 + -0.9x2 = 0.0 + -19.15
-0.9x2 = 0.0 + -19.15

Combine like terms: 0.0 + -19.15 = -19.15
-0.9x2 = -19.15

Divide each side by '-0.9'.
x2 = 21.27777778

Simplifying
x2 = 21.27777778

Take the square root of each side:
x = {-4.612784168, 4.612784168}