(b+3)(b-15)=0

Solution for (b+3)(b-15)=0 equation:

Simplifying
(b + 3)(b + -15) = 0

Reorder the terms:
(3 + b)(b + -15) = 0

Reorder the terms:
(3 + b)(-15 + b) = 0

Multiply (3 + b) * (-15 + b)
(3(-15 + b) + b(-15 + b)) = 0
((-15 * 3 + b * 3) + b(-15 + b)) = 0
((-45 + 3b) + b(-15 + b)) = 0
(-45 + 3b + (-15 * b + b * b)) = 0
(-45 + 3b + (-15b + b2)) = 0

Combine like terms: 3b + -15b = -12b
(-45 + -12b + b2) = 0

Solving
-45 + -12b + b2 = 0

Solving for variable 'b'.

Factor a trinomial.
(-3 + -1b)(15 + -1b) = 0

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

Simplifying
-3 + -1b = 0

Solving
-3 + -1b = 0

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

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

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

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

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

Simplifying
b = -3
Subproblem 2
Set the factor '(15 + -1b)' equal to zero and attempt to solve:

Simplifying
15 + -1b = 0

Solving
15 + -1b = 0

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

Add '-15' to each side of the equation.
15 + -15 + -1b = 0 + -15

Combine like terms: 15 + -15 = 0
0 + -1b = 0 + -15
-1b = 0 + -15

Combine like terms: 0 + -15 = -15
-1b = -15

Divide each side by '-1'.
b = 15

Simplifying
b = 15
Solution
b = {-3, 15}