(3u+1)(3-u)=0

Solution for (3u+1)(3-u)=0 equation:

Simplifying
(3u + 1)(3 + -1u) = 0

Reorder the terms:
(1 + 3u)(3 + -1u) = 0

Multiply (1 + 3u) * (3 + -1u)
(1(3 + -1u) + 3u * (3 + -1u)) = 0
((3 * 1 + -1u * 1) + 3u * (3 + -1u)) = 0
((3 + -1u) + 3u * (3 + -1u)) = 0
(3 + -1u + (3 * 3u + -1u * 3u)) = 0
(3 + -1u + (9u + -3u2)) = 0

Combine like terms: -1u + 9u = 8u
(3 + 8u + -3u2) = 0

Solving
3 + 8u + -3u2 = 0

Solving for variable 'u'.

Factor a trinomial.
(3 + -1u)(1 + 3u) = 0

Subproblem 1
Set the factor '(3 + -1u)' equal to zero and attempt to solve:

Simplifying
3 + -1u = 0

Solving
3 + -1u = 0

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

Add '-3' to each side of the equation.
3 + -3 + -1u = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -1u = 0 + -3
-1u = 0 + -3

Combine like terms: 0 + -3 = -3
-1u = -3

Divide each side by '-1'.
u = 3

Simplifying
u = 3
Subproblem 2
Set the factor '(1 + 3u)' equal to zero and attempt to solve:

Simplifying
1 + 3u = 0

Solving
1 + 3u = 0

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

Add '-1' to each side of the equation.
1 + -1 + 3u = 0 + -1

Combine like terms: 1 + -1 = 0
0 + 3u = 0 + -1
3u = 0 + -1

Combine like terms: 0 + -1 = -1
3u = -1

Divide each side by '3'.
u = -0.3333333333

Simplifying
u = -0.3333333333
Solution
u = {3, -0.3333333333}