(4+u)(5u-9)=0

Solution for (4+u)(5u-9)=0 equation:

Simplifying
(4 + u)(5u + -9) = 0

Reorder the terms:
(4 + u)(-9 + 5u) = 0

Multiply (4 + u) * (-9 + 5u)
(4(-9 + 5u) + u(-9 + 5u)) = 0
((-9 * 4 + 5u * 4) + u(-9 + 5u)) = 0
((-36 + 20u) + u(-9 + 5u)) = 0
(-36 + 20u + (-9 * u + 5u * u)) = 0
(-36 + 20u + (-9u + 5u2)) = 0

Combine like terms: 20u + -9u = 11u
(-36 + 11u + 5u2) = 0

Solving
-36 + 11u + 5u2 = 0

Solving for variable 'u'.

Factor a trinomial.
(-4 + -1u)(9 + -5u) = 0

Subproblem 1
Set the factor '(-4 + -1u)' equal to zero and attempt to solve:

Simplifying
-4 + -1u = 0

Solving
-4 + -1u = 0

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

Add '4' to each side of the equation.
-4 + 4 + -1u = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -1u = 0 + 4
-1u = 0 + 4

Combine like terms: 0 + 4 = 4
-1u = 4

Divide each side by '-1'.
u = -4

Simplifying
u = -4
Subproblem 2
Set the factor '(9 + -5u)' equal to zero and attempt to solve:

Simplifying
9 + -5u = 0

Solving
9 + -5u = 0

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

Add '-9' to each side of the equation.
9 + -9 + -5u = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -5u = 0 + -9
-5u = 0 + -9

Combine like terms: 0 + -9 = -9
-5u = -9

Divide each side by '-5'.
u = 1.8

Simplifying
u = 1.8
Solution
u = {-4, 1.8}