4x^2-21=0

Solution for 4x^2-21=0 equation:

Simplifying
4x2 + -21 = 0

Reorder the terms:
-21 + 4x2 = 0

Solving
-21 + 4x2 = 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 + 4x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 4x2 = 0 + 21
4x2 = 0 + 21

Combine like terms: 0 + 21 = 21
4x2 = 21

Divide each side by '4'.
x2 = 5.25

Simplifying
x2 = 5.25

Take the square root of each side:
x = {-2.291287847, 2.291287847}