3x^2+9-84=0

Solution for 3x^2+9-84=0 equation:

Simplifying
3x2 + 9 + -84 = 0

Reorder the terms:
9 + -84 + 3x2 = 0

Combine like terms: 9 + -84 = -75
-75 + 3x2 = 0

Solving
-75 + 3x2 = 0

Solving for variable 'x'.

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

Add '75' to each side of the equation.
-75 + 75 + 3x2 = 0 + 75

Combine like terms: -75 + 75 = 0
0 + 3x2 = 0 + 75
3x2 = 0 + 75

Combine like terms: 0 + 75 = 75
3x2 = 75

Divide each side by '3'.
x2 = 25

Simplifying
x2 = 25

Take the square root of each side:
x = {-5, 5}