3(u+7)(-u+3)=0

Solution for 3(u+7)(-u+3)=0 equation:

Simplifying
3(u + 7)(-1u + 3) = 0

Reorder the terms:
3(7 + u)(-1u + 3) = 0

Reorder the terms:
3(7 + u)(3 + -1u) = 0

Multiply (7 + u) * (3 + -1u)
3(7(3 + -1u) + u(3 + -1u)) = 0
3((3 * 7 + -1u * 7) + u(3 + -1u)) = 0
3((21 + -7u) + u(3 + -1u)) = 0
3(21 + -7u + (3 * u + -1u * u)) = 0
3(21 + -7u + (3u + -1u2)) = 0

Combine like terms: -7u + 3u = -4u
3(21 + -4u + -1u2) = 0
(21 * 3 + -4u * 3 + -1u2 * 3) = 0
(63 + -12u + -3u2) = 0

Solving
63 + -12u + -3u2 = 0

Solving for variable 'u'.

Factor out the Greatest Common Factor (GCF), '3'.
3(21 + -4u + -1u2) = 0

Factor a trinomial.
3((3 + -1u)(7 + u)) = 0

Ignore the factor 3.
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 '(7 + u)' equal to zero and attempt to solve:

Simplifying
7 + u = 0

Solving
7 + u = 0

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

Add '-7' to each side of the equation.
7 + -7 + u = 0 + -7

Combine like terms: 7 + -7 = 0
0 + u = 0 + -7
u = 0 + -7

Combine like terms: 0 + -7 = -7
u = -7

Simplifying
u = -7
Solution
u = {3, -7}