(y-3)2=21

Solution for (y-3)2=21 equation:

Simplifying
(y + -3) * 2 = 21

Reorder the terms:
(-3 + y) * 2 = 21

Reorder the terms for easier multiplication:
2(-3 + y) = 21
(-3 * 2 + y * 2) = 21
(-6 + 2y) = 21

Solving
-6 + 2y = 21

Solving for variable 'y'.

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

Add '6' to each side of the equation.
-6 + 6 + 2y = 21 + 6

Combine like terms: -6 + 6 = 0
0 + 2y = 21 + 6
2y = 21 + 6

Combine like terms: 21 + 6 = 27
2y = 27

Divide each side by '2'.
y = 13.5

Simplifying
y = 13.5