7-2(4x^2-16)=21

Solution for 7-2(4x^2-16)=21 equation:

Simplifying
7 + -2(4x2 + -16) = 21

Reorder the terms:
7 + -2(-16 + 4x2) = 21
7 + (-16 * -2 + 4x2 * -2) = 21
7 + (32 + -8x2) = 21

Combine like terms: 7 + 32 = 39
39 + -8x2 = 21

Solving
39 + -8x2 = 21

Solving for variable 'x'.

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

Add '-39' to each side of the equation.
39 + -39 + -8x2 = 21 + -39

Combine like terms: 39 + -39 = 0
0 + -8x2 = 21 + -39
-8x2 = 21 + -39

Combine like terms: 21 + -39 = -18
-8x2 = -18

Divide each side by '-8'.
x2 = 2.25

Simplifying
x2 = 2.25

Take the square root of each side:
x = {-1.5, 1.5}