You are Here: Home >< Maths

completing the square Watch

1. im on the last step of completing the square when a>1

when multiplying 2 with everything, where did the denominator go from 15/2?and if the denominator was not a 2, let's say it was 15/10, then would that become 15/5? is my logic right or am i missing something
2. its dominator gets divided so 2/2=1
3. (Original post by ihatePE)
im on the last step of completing the square when a>1

when multiplying 2 with everything, where did the denominator go from 15/2?and if the denominator was not a 2, let's say it was 15/10, then would that become 15/5? is my logic right or am i missing something
The 2 at the front is to multiply everything. So 2 x 15/2 = 15.

But you're learning how to do this by working from the marking scheme?
4. (Original post by offhegoes)
The 2 at the front is to multiply everything. So 2 x 15/2 = 15.

But you're learning how to do this by working from the marking scheme?
no im learning C1 and C2 from the wjec revision and study guide along with my notes from the step-up classes and youtube videos and TSR xD
5. If you have a general quadratic
when completing the square you get .
So if you have
you complete the square as follows
.
You multiply the 4 by 2 as there is a 2 out front to the left of the brackets.
6. (Original post by fatima1998)
its dominator gets divided so 2/2=1
i see, im not used to multiplying out like this never seen anything like it at gcse
7. I mean... you kinda double 15 halves... that's like doubling a halve, then multiplying that 15 times....

When you multiply everything by 2, the 15/2 goes to (15x2)/2 where the 2's cancel. Surely you should know this without question?
8. (Original post by ihatePE)
i see, im not used to multiplying out like this never seen anything like it at gcse
OMGGGG its GCSEs that means i still can do it its just like you 2*15/2
9. (Original post by ihatePE)
i see, im not used to multiplying out like this never seen anything like it at gcse
2 x 15/2....

Trying writing 2 as 2/1.

So this becomes 2/1 x 15/2

Top times top over bottom times bottom. Try cross-cancelling first to see why the 2 disappears though.

So many pupils of your level have such poor fraction skills! (No offence, just an observation).
10. (Original post by offhegoes)
2 x 15/2....

Trying writing 2 as 2/1.

So this becomes 2/1 x 15/2

Top times top over bottom times bottom. Try cross-cancelling first to see why the 2 disappears though.

So many pupils of your level have such poor fraction skills! (No offence, just an observation).
I'm more surprised by the "never seen anything like it at gcse".. I've done my GCSE's just over 2 years ago and this should be common knowledge, shouldn't it? I'm pretty sure pupils are expected to multiply fractions in one way or another.
11. (Original post by offhegoes)
2 x 15/2....

Trying writing 2 as 2/1.

So this becomes 2/1 x 15/2

Top times top over bottom times bottom. Try cross-cancelling first to see why the 2 disappears though.

So many pupils of your level have such poor fraction skills! (No offence, just an observation).
i know, fractions scare me, especially those equations
i had a question similar to this in my gcse and i was all over the place, to this day i still dont know how you would solve these things, like what do you do with the 31/6 denominator???

(Original post by RDKGames)
I mean... you kinda double 15 halves... that's like doubling a halve, then multiplying that 15 times....

When you multiply everything by 2, the 15/2 goes to (15x2)/2 where the 2's cancel. Surely you should know this without question?
i understand it now that you've written it like (15x2)/2, because in my head i saw it as (15x2)/(2x2)
12. (Original post by ihatePE)
i know, fractions scare me, especially those equations
i had a question similar to this in my gcse and i was all over the place, to this day i still dont know how you would solve these things, like what do you do with the 31/6 denominator???

i understand it now that you've written it like (15x2)/2, because in my head i saw it as (15x2)/(2x2)
I see. When multiplying a fraction by an integer, only the numerator gets multiplied. When a fraction is multiplied by a fraction, the numerators and denominators multiply respectively.

However if you add fractions, you want to get them under the same denominator in which case you are free to combine them. In the example you posted, you only need to multiply the first term by 3 (top and bottom) and the second by 2. The reason behind multiplying numerator AND denominator is so you can preserve the equality of the quantity (or keep the value of the expression the same), while maintaining a different denominator. Now you have everything over 6 at which point you just multiply throughout by 6 which makes the fractions cancel and then you're dealing with a simple linear equation.

Once you get better, you'll just realise that you can simply multiply the whole equation by 6. As 2 and 3 are factors of 6, they will go away and you will be left with no different denominators.
13. (Original post by ihatePE)
i know, fractions scare me, especially those equations
i had a question similar to this in my gcse and i was all over the place, to this day i still dont know how you would solve these things, like what do you do with the 31/6 denominator???

i understand it now that you've written it like (15x2)/2, because in my head i saw it as (15x2)/(2x2)
When there are fractions in denominators it is best just to multiply by the denominator of the fraction in the denominator - if that makes sense.
So .
14. (Original post by RDKGames)
I see. When multiplying a fraction by an integer, only the numerator gets multiplied. When a fraction is multiplied by a fraction, the numerators and denominators multiply respectively.

However if you add fractions, you want to get them under the same denominator in which case you are free to combine them. In the example you posted, you only need to multiply the first term by 3 (top and bottom) and the second by 2. The reason behind multiplying numerator AND denominator is so you can preserve the equality of the quantity (or keep the value of the expression the same), while maintaining a different denominator. Now you have everything over 6 at which point you just multiply throughout by 6 which makes the fractions cancel and then you're dealing with a simple linear equation.
(Original post by B_9710)
When there are fractions in denominators it is best just to multiply by the denominator of the fraction in the denominator - if that makes sense.
So .
thank you!!! i get a lot of things but it's these small things that gets blurry as more information pile in
15. (Original post by RDKGames)
I see. When multiplying a fraction by an integer, only the numerator gets multiplied. When a fraction is multiplied by a fraction, the numerators and denominators multiply respectively.

However if you add fractions, you want to get them under the same denominator in which case you are free to combine them. In the example you posted, you only need to multiply the first term by 3 (top and bottom) and the second by 2. The reason behind multiplying numerator AND denominator is so you can preserve the equality of the quantity (or keep the value of the expression the same), while maintaining a different denominator. Now you have everything over 6 at which point you just multiply throughout by 6 which makes the fractions cancel and then you're dealing with a simple linear equation.

Once you get better, you'll just realise that you can simply multiply the whole equation by 6. As 2 and 3 are factors of 6, they will go away and you will be left with no different denominators.
can you check if this is correct
simplify:
2+√5 / 3-√5

i got 11+5√5 / 4
16. (Original post by ihatePE)
can you check if this is correct
simplify:
2+√5 / 3-√5

i got 11+5√5 / 4
Yep.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: July 2, 2016
Today on TSR

Last-minute PS help

100s of personal statements examples here

More pressure for kinky sex?

Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants

Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.