Question

Factor the trinomial. x^2-4x-5

Answer 1

Answer: Choice C.  (x+1)(x-5)

We need to find two numbers that

• Multiply to -5 (last term)
• Add to -4 (middle coefficient)

Through trial and error, those two numbers are 1 and -5

• 1 times -5 = -5
• 1 plus -5 = -4

So this means x^2-4x-5 factors to (x+1)(x-5)

This is the same as (x-5)(x+1) since the order of multiplication doesn't matter.