The Student Room Group

as maths help

ok please someone help the question is 18x^2-12x/18x^2-8
Original post by shayankurdboy
ok please someone help the question is 18x^2-12x/18x^2-8


bump
These are just power rules? You should really know these if you're taking as maths.


Posted from TSR Mobile
Original post by shayankurdboy
bump


bump
Reply 4
Original post by shayankurdboy
ok please someone help the question is 18x^2-12x/18x^2-8


Look for a common between the numerator and denomintor so you can cancel them both out.

Ill help ya with the top part

18x212x[br]Highestcommonfactorof6:6(3x22x)[br]Anotherfactorofx:6x(3x2)18x^2-12x[br]Highest common factor of 6: 6(3x^2-2x)[br]Another factor of x: 6x(3x-2)

Basically after working that out, alarm bells should be ringing that the denomintor should either be a multiple of 2, (3x-2) or a multiple of x.

You'll get better at these sorta stuff once you get into the swings of questions and start spotting the general idea!
(edited 9 years ago)
Reply 5
Original post by shayankurdboy
ok please someone help the question is 18x^2-12x/18x^2-8


That's not a question, it's just an expression.

What are you supposed to be doing with it?
Original post by davros
That's not a question, it's just an expression.

What are you supposed to be doing with it?

thanks for the help
Original post by Jkizer
Look for a common between the numerator and denomintor so you can cancel them both out.

Ill help ya with the top part

18x212x[br]Highestcommonfactorof6:6(3x22x)[br]Anotherfactorofx:6x(3x2)18x^2-12x[br]Highest common factor of 6: 6(3x^2-2x)[br]Another factor of x: 6x(3x-2)

Basically after working that out, alarm bells should be ringing that the denomintor should either be a multiple of 2, (3x-2) or a multiple of x.

You'll get better at these sorta stuff once you get into the swings of questions and start spotting the general idea!

cant i just cancel out the two 18^2.
Original post by shayankurdboy
cant i just cancel out the two 18^2.


Your sarcasm aimed at Davros will not win you any friends

He asked you a question

We can guess that you are meant to simplify but it will help in future if you give full questions


So - with regard to your cancelling the 18x218x^2 terms - No

Consider 3+23+7\dfrac{3+2}{3+7} cancelling the 3s would clearly give a different answer


You need to factorise the numerator and denominator and look for common factor(s) to cancel
Reply 9
Original post by shayankurdboy
ok please someone help the question is 18x^2-12x/18x^2-8


This isn't a question. Are you supposed to simplify this, or what?
Original post by james22
This isn't a question. Are you supposed to simplify this, or what?


ok guys sorry for not making this clear yes its to simplify fully
Reply 11
Original post by shayankurdboy
cant i just cancel out the two 18^2.

Yeah thats a common mistake, that even i use to make.

If you go back to basics, when you first did algebra the teacher would usually say that x could be any value.
So just for the sake of making it simple, lets just assume x=2
[br][br]18(2)212(2)=>7224=48[br]18(2)28=>728=64[br] [br][br]18(2)^2-12(2) => 72-24 = 48[br]18(2)^2-8 => 72-8 = 64[br]
So obviously they do not cancel each other directly, so you couldnt just take out the 18x^2 straight out. However if you took out a factor of 2 out, they could cancel out

In C1, when your doing these sorta questions it can be fairly easy to make mistakes. So i would (if i have time) to substitute an easy x number like 1 or 2 into the original and the simplified version. If they both are the same, then its very likely that your answer is correct :smile:. I found myself doing this sort of stuff through to A2 maths which really helped!
(edited 9 years ago)

Quick Reply

Latest