Question

Factor each trinomial below. Please show your work and check your answer. (1 point each)
1. x^2 – 8x + 15
2. a^2 – a – 20
3. a^2 – 5a – 20
4. a^2 + 12ab + 27b^2
5. 2a^2 + 30a + 100

*I got (x - 5)(x - 3) for the first one is that correct? I'm stuck on the second one..Please help!

Answer 1

Yep :) You are right!

Answer 2

For the second one:
You need to find two factors of -20 that have product -20 and sum -1

Answer 3

Can you do that?

Answer 4

In general if you have
ax^2+bx+c
You need to find two factors of a*c that have product a*c and sum b
If a=1, then you just place those numbers in the following blanks (x-___)(x-___)
If a= something other 1, it is a little more complicated.
You will need to replace the middle term with ___x+___x
where those blanks are filled by the numbers you just found
Then you factor by grouping

Answer 5

yea i know that but i don't know how to find the factors for this one

Answer 6

please help(: @myininaya

Answer 7

wow... this is the same problem set that i just helped someone with!!!!!!

Answer 8

a^2 – a – 20.
per myininaya's explanation, the two numbers that multiply to give you -20a^2, and add to give you -a are -5a and +4a

Answer 9

you'd write it as
a^2 -a -20
a^2 -5a+4a-20
a(a-5)+4(a-5)
(a-5)(a+4)

Answer 10

Okay , well i actually called my teacher and she explained it to me but thanks!(: