Question

Factor each trinomial below. Please show your work and check your answer.

x2 – 8x + 15
a2 – a – 20
a2 – 5a – 20
a2 + 12ab + 27b2
2a2 + 30a + 100

Answer 1

Check your answers against the following list:\[\left\{(x-5) (x-3),(a-5) (a+4),a^2-5 a-20,(a+3 b) (a+9 b),2 (a+5) (a+10)\right\} \]The third expression cannot be factored.

Answer 2

x^2-8x+15
=>x^2+3x-5x+15
=>x(x+3)-5(x-3)
=>(x-5)(x^2-9)

Answer 3

a2 – a – 20
a2-5a+4a-20
(a+4)(a-5)

for a2 – 5a – 20 use (-b+b2-4ac)/2a ,(-b-b2-4ac)/2a

for a2 + 12ab + 27b2=(a+3b)(a+9b)

for 2a2 + 30a + 100=(2a+10)(a+10)