2x^2-9=21

Solution for 2x^2-9=21 equation:

Simplifying
2x2 + -9 = 21

Reorder the terms:
-9 + 2x2 = 21

Solving
-9 + 2x2 = 21

Solving for variable 'x'.

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

Add '9' to each side of the equation.
-9 + 9 + 2x2 = 21 + 9

Combine like terms: -9 + 9 = 0
0 + 2x2 = 21 + 9
2x2 = 21 + 9

Combine like terms: 21 + 9 = 30
2x2 = 30

Divide each side by '2'.
x2 = 15

Simplifying
x2 = 15

Take the square root of each side:
x = {-3.872983346, 3.872983346}