81=(25x)(x)

Solution for 81=(25x)(x) equation:

Simplifying
81 = (25x)(x)

Remove parenthesis around (25x)
81 = 25x(x)

Multiply x * x
81 = 25x2

Solving
81 = 25x2

Solving for variable 'x'.

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

Add '-25x2' to each side of the equation.
81 + -25x2 = 25x2 + -25x2

Combine like terms: 25x2 + -25x2 = 0
81 + -25x2 = 0

Add '-81' to each side of the equation.
81 + -81 + -25x2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -25x2 = 0 + -81
-25x2 = 0 + -81

Combine like terms: 0 + -81 = -81
-25x2 = -81

Divide each side by '-25'.
x2 = 3.24

Simplifying
x2 = 3.24

Take the square root of each side:
x = {-1.8, 1.8}