Maths Help pl0x. Quite easy, i think

[J03]

OK, So i have test come monday. I've just moved school's, and they have covered things i hadnt done in my old school. Please dont laugh at me about this, i know it's supposed to be pretty simple... But i'm having trouble with Factoring.
I can do some easyer things, but i've got some questions below:

2h^2-15h-27

2k^2-15k+27

6a^2+7a-5

To practice with. I could just use an algebra calculator thingimabob, but that wouldnt teach me anything. Could somone answer these for me, and explain how they did it?

Thanks

j03

 

[TheLastWolf]

(2h+3)(h-9)
(2k-9)(k-3)
(3a+5)(2a-1)
Always find the LCM of the outside number first
IE
6a^2+7a-5
'outside number' is 6
LCM is 3 and 2.
-5 is the Multiple and +7a is the sum.
So from just that I know it will be (3a )(2a )
Which I would write on the paper first, since you find the LCM first.
Then I would go (3a+5) because 15a + 3a = 18a not 7a.
So the other half has to be (2a-1) because the multiple is negative and a negative*positive is always a negative.

breakdown of the other two.
2h^2-15h-27
LCM of 2 is 2 and 1.
So
(2h )(h )
Multiple is 27. Sum is 15.
9*3 = 27
One has to be positive one has to be negative.
+6-9=-3 which isnt 15 So can't be (2h-9)(h+3)
So it has to be (2h+3)(h-9)

then the other question is the same question but the multiple is +27 not -27. So they both have to be negative. And since -18-3 =-21 not 15 it has to be
(2k-9)(k-3)

 

[TheLastWolf]

Broke it down for you.

 

[J03]

Thank's Man. I will look over that in a bit. I really appreciate it. +1

 

[JogaBonito1502]

Dude, what the lastwolf said pretty much sums it up. If you're good at doing stuff in your head then it is much quicker to do simple trial and errors mentally to narrow down your opitions rather than writing all that stuff out. Once I learned the principle I just had a calculator do it for me.

 

[Le 3eme oeil]

Dude, what the lastwolf said pretty much sums it up. If you're good at doing stuff in your head then it is much quicker to do simple trial and errors mentally to narrow down your opitions rather than writing all that stuff out. Once I learned the principle I just had a calculator do it for me.

Hey how long have you had a reputation beyond repute? I knew you had 2 bars is that automatically reputation beyond repute?

 

[JogaBonito1502]

Dude I have no idea. One day I was at 98 rep. points, next thing I log on I'm at 136. So, I can't really tell you. Sorry mate.

 

[TheLastWolf]

Dude, what the lastwolf said pretty much sums it up. If you're good at doing stuff in your head then it is much quicker to do simple trial and errors mentally to narrow down your opitions rather than writing all that stuff out. Once I learned the principle I just had a calculator do it for me.

Yeah, I do it all in my head. It was harder to explain than actually doing the questions.