(3y+9)(3y-9)=

Solution for (3y+9)(3y-9)= equation:

Simplifying
(3y + 9)(3y + -9) = 0

Reorder the terms:
(9 + 3y)(3y + -9) = 0

Reorder the terms:
(9 + 3y)(-9 + 3y) = 0

Multiply (9 + 3y) * (-9 + 3y)
(9(-9 + 3y) + 3y * (-9 + 3y)) = 0
((-9 * 9 + 3y * 9) + 3y * (-9 + 3y)) = 0
((-81 + 27y) + 3y * (-9 + 3y)) = 0
(-81 + 27y + (-9 * 3y + 3y * 3y)) = 0
(-81 + 27y + (-27y + 9y2)) = 0

Combine like terms: 27y + -27y = 0
(-81 + 0 + 9y2) = 0
(-81 + 9y2) = 0

Solving
-81 + 9y2 = 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 + 9y2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + 9y2 = 0 + 81
9y2 = 0 + 81

Combine like terms: 0 + 81 = 81
9y2 = 81

Divide each side by '9'.
y2 = 9

Simplifying
y2 = 9

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