.5a^2+3=21

Solution for .5a^2+3=21 equation:

Simplifying
0.5a2 + 3 = 21

Reorder the terms:
3 + 0.5a2 = 21

Solving
3 + 0.5a2 = 21

Solving for variable 'a'.

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

Add '-3' to each side of the equation.
3 + -3 + 0.5a2 = 21 + -3

Combine like terms: 3 + -3 = 0
0 + 0.5a2 = 21 + -3
0.5a2 = 21 + -3

Combine like terms: 21 + -3 = 18
0.5a2 = 18

Divide each side by '0.5'.
a2 = 36

Simplifying
a2 = 36

Take the square root of each side:
a = {-6, 6}