3x^2-x^2-72=0

Solution for 3x^2-x^2-72=0 equation:

Simplifying
3x2 + -1x2 + -72 = 0

Reorder the terms:
-72 + 3x2 + -1x2 = 0

Combine like terms: 3x2 + -1x2 = 2x2
-72 + 2x2 = 0

Solving
-72 + 2x2 = 0

Solving for variable 'x'.

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

Add '72' to each side of the equation.
-72 + 72 + 2x2 = 0 + 72

Combine like terms: -72 + 72 = 0
0 + 2x2 = 0 + 72
2x2 = 0 + 72

Combine like terms: 0 + 72 = 72
2x2 = 72

Divide each side by '2'.
x2 = 36

Simplifying
x2 = 36

Take the square root of each side:
x = {-6, 6}