9=21x^2

Solution for 9=21x^2 equation:

Simplifying
9 = 21x2

Solving
9 = 21x2

Solving for variable 'x'.

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

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

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

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

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

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

Divide each side by '-21'.
x2 = 0.4285714286

Simplifying
x2 = 0.4285714286

Take the square root of each side:
x = {-0.654653671, 0.654653671}