(3x)(3x)-21=0

Solution for (3x)(3x)-21=0 equation:

Simplifying
(3x)(3x) + -21 = 0

Remove parenthesis around (3x)
3x(3x) + -21 = 0

Remove parenthesis around (3x)
3x * 3x + -21 = 0

Reorder the terms for easier multiplication:
3 * 3x * x + -21 = 0

Multiply 3 * 3
9x * x + -21 = 0

Multiply x * x
9x2 + -21 = 0

Reorder the terms:
-21 + 9x2 = 0

Solving
-21 + 9x2 = 0

Solving for variable 'x'.

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

Add '21' to each side of the equation.
-21 + 21 + 9x2 = 0 + 21

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

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

Divide each side by '9'.
x2 = 2.333333333

Simplifying
x2 = 2.333333333

Take the square root of each side:
x = {-1.527525232, 1.527525232}