81-2x^2=7x^2

Solution for 81-2x^2=7x^2 equation:

Simplifying
81 + -2x2 = 7x2

Solving
81 + -2x2 = 7x2

Solving for variable 'x'.

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

Add '-7x2' to each side of the equation.
81 + -2x2 + -7x2 = 7x2 + -7x2

Combine like terms: -2x2 + -7x2 = -9x2
81 + -9x2 = 7x2 + -7x2

Combine like terms: 7x2 + -7x2 = 0
81 + -9x2 = 0

Add '-81' to each side of the equation.
81 + -81 + -9x2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -9x2 = 0 + -81
-9x2 = 0 + -81

Combine like terms: 0 + -81 = -81
-9x2 = -81

Divide each side by '-9'.
x2 = 9

Simplifying
x2 = 9

Take the square root of each side:
x = {-3, 3}