(z+9)(z-9)=

Solution for (z+9)(z-9)= equation:

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

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

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

Multiply (9 + z) * (-9 + z)
(9(-9 + z) + z(-9 + z)) = 0
((-9 * 9 + z * 9) + z(-9 + z)) = 0
((-81 + 9z) + z(-9 + z)) = 0
(-81 + 9z + (-9 * z + z * z)) = 0
(-81 + 9z + (-9z + z2)) = 0

Combine like terms: 9z + -9z = 0
(-81 + 0 + z2) = 0
(-81 + z2) = 0

Solving
-81 + z2 = 0

Solving for variable 'z'.

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

Add '81' to each side of the equation.
-81 + 81 + z2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + z2 = 0 + 81
z2 = 0 + 81

Combine like terms: 0 + 81 = 81
z2 = 81

Simplifying
z2 = 81

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