0=x^2-21

Solution for 0=x^2-21 equation:

Simplifying
0 = x2 + -21

Reorder the terms:
0 = -21 + x2

Solving
0 = -21 + x2

Solving for variable 'x'.

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

Add '-1x2' to each side of the equation.
0 + -1x2 = -21 + x2 + -1x2
Remove the zero:
-1x2 = -21 + x2 + -1x2

Combine like terms: x2 + -1x2 = 0
-1x2 = -21 + 0
-1x2 = -21

Divide each side by '-1'.
x2 = 21

Simplifying
x2 = 21

Take the square root of each side:
x = {-4.582575695, 4.582575695}