Factor each expression

1) 4a^2-16ab^3+8ab^2c 2) n^2+8n+15

3) g^2-9g+20

4) z^2-7z-30

5) 4y^3-36y

1 - since everything includes 4a, we can factor that to get 4a (a-4b^3+2b^2c)

2 - since 5 and 3 add to 8 and multiply to 15, we can do (n+5) (n+3)

3 - since - 5 and - 4 add to - 9 and multiply to 20, we can do (g-5) (g-4)

4 - since - 10 and 3 add to - 7 and multiply to 30, we can do (z-10) (z+3)

5 - we can factor out 4y to get 4y (y^2-9).

I got the numbers in 2, 3, and 4 with a guesstimating and checking approach