81=y^2+2y^2

Solution for 81=y^2+2y^2 equation:

Simplifying
81 = y2 + 2y2

Combine like terms: y2 + 2y2 = 3y2
81 = 3y2

Solving
81 = 3y2

Solving for variable 'y'.

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

Add '-3y2' to each side of the equation.
81 + -3y2 = 3y2 + -3y2

Combine like terms: 3y2 + -3y2 = 0
81 + -3y2 = 0

Add '-81' to each side of the equation.
81 + -81 + -3y2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -3y2 = 0 + -81
-3y2 = 0 + -81

Combine like terms: 0 + -81 = -81
-3y2 = -81

Divide each side by '-3'.
y2 = 27

Simplifying
y2 = 27

Take the square root of each side:
y = {-5.196152423, 5.196152423}