(9-u)(9+u)=

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

Simplifying
(9 + -1u)(9 + u) = 0

Multiply (9 + -1u) * (9 + u)
(9(9 + u) + -1u * (9 + u)) = 0
((9 * 9 + u * 9) + -1u * (9 + u)) = 0
((81 + 9u) + -1u * (9 + u)) = 0
(81 + 9u + (9 * -1u + u * -1u)) = 0
(81 + 9u + (-9u + -1u2)) = 0

Combine like terms: 9u + -9u = 0
(81 + 0 + -1u2) = 0
(81 + -1u2) = 0

Solving
81 + -1u2 = 0

Solving for variable 'u'.

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

Add '-81' to each side of the equation.
81 + -81 + -1u2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -1u2 = 0 + -81
-1u2 = 0 + -81

Combine like terms: 0 + -81 = -81
-1u2 = -81

Divide each side by '-1'.
u2 = 81

Simplifying
u2 = 81

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