21=2x^2+3

Solution for 21=2x^2+3 equation:

Simplifying
21 = 2x2 + 3

Reorder the terms:
21 = 3 + 2x2

Solving
21 = 3 + 2x2

Solving for variable 'x'.

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

Add '-2x2' to each side of the equation.
21 + -2x2 = 3 + 2x2 + -2x2

Combine like terms: 2x2 + -2x2 = 0
21 + -2x2 = 3 + 0
21 + -2x2 = 3

Add '-21' to each side of the equation.
21 + -21 + -2x2 = 3 + -21

Combine like terms: 21 + -21 = 0
0 + -2x2 = 3 + -21
-2x2 = 3 + -21

Combine like terms: 3 + -21 = -18
-2x2 = -18

Divide each side by '-2'.
x2 = 9

Simplifying
x2 = 9

Take the square root of each side:
x = {-3, 3}