Find the GCF (Greatest Common Factor)
GCF = 3
Factor out the GCF ( Write the GCF first. Then, in parentheses, divide each term by the GCF)
3(3x^2/3 + -12x/3 - 15/3)
Simplify each term in parentheses
3(x^2 - 4x - 5)
Factor x^2 - 4x - 5
3(x - 5)(x + 1)