(y-9)(y+9)=0

Solution for (y-9)(y+9)=0 equation:

Simplifying
(y + -9)(y + 9) = 0

Reorder the terms:
(-9 + y)(y + 9) = 0

Reorder the terms:
(-9 + y)(9 + y) = 0

Multiply (-9 + y) * (9 + y)
(-9(9 + y) + y(9 + y)) = 0
((9 * -9 + y * -9) + y(9 + y)) = 0
((-81 + -9y) + y(9 + y)) = 0
(-81 + -9y + (9 * y + y * y)) = 0
(-81 + -9y + (9y + y2)) = 0

Combine like terms: -9y + 9y = 0
(-81 + 0 + y2) = 0
(-81 + y2) = 0

Solving
-81 + y2 = 0

Solving for variable 'y'.

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

Add '81' to each side of the equation.
-81 + 81 + y2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + y2 = 0 + 81
y2 = 0 + 81

Combine like terms: 0 + 81 = 81
y2 = 81

Simplifying
y2 = 81

Take the square root of each side:
y = {-9, 9}