x^2+2x^2-69-18=0

Solution for x^2+2x^2-69-18=0 equation:

Simplifying
x2 + 2x2 + -69 + -18 = 0

Reorder the terms:
-69 + -18 + x2 + 2x2 = 0

Combine like terms: -69 + -18 = -87
-87 + x2 + 2x2 = 0

Combine like terms: x2 + 2x2 = 3x2
-87 + 3x2 = 0

Solving
-87 + 3x2 = 0

Solving for variable 'x'.

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

Add '87' to each side of the equation.
-87 + 87 + 3x2 = 0 + 87

Combine like terms: -87 + 87 = 0
0 + 3x2 = 0 + 87
3x2 = 0 + 87

Combine like terms: 0 + 87 = 87
3x2 = 87

Divide each side by '3'.
x2 = 29

Simplifying
x2 = 29

Take the square root of each side:
x = {-5.385164807, 5.385164807}