-15-3a=3a(-a-5)

Solution for -15-3a=3a(-a-5) equation:

Simplifying
-15 + -3a = 3a(-1a + -5)

Reorder the terms:
-15 + -3a = 3a(-5 + -1a)
-15 + -3a = (-5 * 3a + -1a * 3a)
-15 + -3a = (-15a + -3a2)

Solving
-15 + -3a = -15a + -3a2

Solving for variable 'a'.

Combine like terms: -3a + 15a = 12a
-15 + 12a + 3a2 = -15a + -3a2 + 15a + 3a2

Reorder the terms:
-15 + 12a + 3a2 = -15a + 15a + -3a2 + 3a2

Combine like terms: -15a + 15a = 0
-15 + 12a + 3a2 = 0 + -3a2 + 3a2
-15 + 12a + 3a2 = -3a2 + 3a2

Combine like terms: -3a2 + 3a2 = 0
-15 + 12a + 3a2 = 0

Factor out the Greatest Common Factor (GCF), '3'.
3(-5 + 4a + a2) = 0

Factor a trinomial.
3((-5 + -1a)(1 + -1a)) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(-5 + -1a)' equal to zero and attempt to solve:

Simplifying
-5 + -1a = 0

Solving
-5 + -1a = 0

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

Add '5' to each side of the equation.
-5 + 5 + -1a = 0 + 5

Combine like terms: -5 + 5 = 0
0 + -1a = 0 + 5
-1a = 0 + 5

Combine like terms: 0 + 5 = 5
-1a = 5

Divide each side by '-1'.
a = -5

Simplifying
a = -5
Subproblem 2
Set the factor '(1 + -1a)' equal to zero and attempt to solve:

Simplifying
1 + -1a = 0

Solving
1 + -1a = 0

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

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

Combine like terms: 1 + -1 = 0
0 + -1a = 0 + -1
-1a = 0 + -1

Combine like terms: 0 + -1 = -1
-1a = -1

Divide each side by '-1'.
a = 1

Simplifying
a = 1
Solution
a = {-5, 1}