1. x2 – 8x + 15 ?

2.2.a2 – a – 20

Question

1. x2 – 8x + 15 ?

2.2.a2 – a – 20

anonymous · Answer

Help Please ?

anonymous · Answer

so you have to factor right? :)

anonymous · Answer

yes

anonymous · Answer

what two numbers multiply to make 15 and  add up to make 8?

anonymous · Answer

3x5 aand 5+3

anonymous · Answer

okay cool :) u got it!
now we need to set up two binomials$$(x~~~~~~)(x~~~~~~)$$how do we know what signs to use?
the second plus sign in the trinomial means the signs will be the same
how do we know whether positive or negative? 
the first sign is a minus sign meaning they both will be negative$$(x-~~)(x-~~)$$now just put in the numbers$$(x-3)(x-5)$$and theres you have it! :D

anonymous · Answer

wait thats all..? thats the answer? :)

anonymous · Answer

to the first one, yes :)

anonymous · Answer

that was easy lol

anonymous · Answer

It can be shown by other method also..

anonymous · Answer

hey watch this video...its a rap on how to factor...trust me its gonna help a lot :D http://www.youtube.com/watch?v=OFSrINhfNsQ

anonymous · Answer

$$x^2 - 8x + 15$$

$$x^2 - 3x - 5x + 15$$

$$x(x - 3) - 5(x -3)$$

$$(x-3)(x-5)$$

anonymous · Answer

@waterineyes like what other methods? use number 2 as an example please? :)

anonymous · Answer

oh lol nvm

anonymous · Answer

Now solve it for second problem of yours..

I have given you the method..

anonymous · Answer

i hope i helped :)