Does anyone know how to factor trinomials completely? I need to factor: 20a - 2a^ - 18 completely. Here is what I have so far: 2(10A - a^ -9). What do I do next? The solution is: -2(a - 9)(a - 1) but I cannot figure out how to get there.

Question

Does anyone know how to factor trinomials completely?  I need to factor: 20a - 2a^ - 18 completely. Here is what I have so far: 2(10A - a^ -9).  What do I do next? The solution is: -2(a - 9)(a - 1) but I cannot figure out how to get there.

anonymous · Answer

you need to put the a^2 term first

anonymous · Answer

Use reverse FOIL?

anonymous · Answer

I understand I need to put the a ^ 2 first, but I don't understand WHY I need too?? How do you know to put the a ^2 first?

anonymous · Answer

-2a^2 + 20a - 18

factor out a -2
-2(a^2 - 10a + 9)

you need factors of 9 that add to get 10 ----    9 and 1
-2(a - 9)(a - 1)

anonymous · Answer

-2(a^2-10a+9)=0
(a-9)(a-1)=0
a=1,9

anonymous · Answer

the form of a quadratic is ax2+bx+c

anonymous · Answer

great ankur!

anonymous · Answer

thanx

anonymous · Answer

Think about... what 2 numbers times each other equals -9 and added together equals -10.. Also always make sure the a^2 term is positive so it will make the factoring very easy