3x^2+21-90=0

Solution for 3x^2+21-90=0 equation:

Simplifying
3x2 + 21 + -90 = 0

Reorder the terms:
21 + -90 + 3x2 = 0

Combine like terms: 21 + -90 = -69
-69 + 3x2 = 0

Solving
-69 + 3x2 = 0

Solving for variable 'x'.

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

Add '69' to each side of the equation.
-69 + 69 + 3x2 = 0 + 69

Combine like terms: -69 + 69 = 0
0 + 3x2 = 0 + 69
3x2 = 0 + 69

Combine like terms: 0 + 69 = 69
3x2 = 69

Divide each side by '3'.
x2 = 23

Simplifying
x2 = 23

Take the square root of each side:
x = {-4.795831523, 4.795831523}