The Student Room Group

!URGENT! 1 question on Surds! GCSE!

I cant complete this final question could someone help me how to get the final answer which is -5+4√3 (calculator^^)

THX!!!!!!
p.s. its A* Q6
Reply 1
Rationalising means you remove the denominator by multiplying the entire fraction by it, i.e. multiply top and bottom by root 3.
Reply 2
Original post by NikolaT
Rationalising means you remove the denominator by multiplying the entire fraction by it, i.e. multiply top and bottom by root 3.


I know that I've even done the other questions correctly it just this one where i'm doing something wrong and that means i cannot get the right answer.

When I've done what you said I've now got 12-5+3/3 this is where i don't know what to do. :/
(edited 9 years ago)
Original post by moththecat
I know that I've even done the other questions correctly it just this one where i'm doing something wrong and that means i cannot get the right answer.

When I've done what you said I've now got 12-5+3/3 this is where i don't know what to do. :/


When you multiply the numerator by 3\sqrt3 what do you get

Remember you have to multiply both bits
Reply 4
Original post by TenOfThem
When you multiply the numerator by 3\sqrt3 what do you get

Remember you have to multiply both bits

12-59\sqrt9= 12-5+3
(edited 9 years ago)
Original post by moththecat
12-5+9\sqrt9= 12-5+3


The numerator is 12 - 5root3

What do you get when you multiply 12 by root 3

What do you get when you multiply 5root3 by root3 .... You started doing this correctly but then turned 5root9 into 5+root9 ... Why
(edited 9 years ago)
Reply 6
Original post by TenOfThem
The numerator is 12 - 5root3

What do you get when you multiply 12 by root 3

What do you get when you multiply 5root3 by root3 .... You started doing this correctly but then turned 5root9 into 5+root9 ... Why

A) What do you get when you multiply 12 by root 3 = 12√3
B)
What do you get when you multiply 5root3 by root3 = 5√9

so what now?:smile:
Original post by moththecat
A) What do you get when you multiply 12 by root 3 = 12√3
B)
What do you get when you multiply 5root3 by root3 = 5√9

so what now?:smile:


You know what root9 is so simplify 5root9

Then divide both bits by 3 since you had 3 in the denominator
Reply 8
Original post by moththecat
I cant complete this final question could someone help me how to get the final answer which is -5+4√3 (calculator^^)

THX!!!!!!
p.s. its A* Q6

Hope this helps!
Original post by SaiDuc
Hope this helps!


Presumably you are unaware that full solutions are against the forum guidelines
Reply 10
Original post by TenOfThem
You know what root9 is so simplify 5root9

Then divide both bits by 3 since you had 3 in the denominator


That wont get me -5+4√3 what you said will get me 12-5√3
Original post by moththecat
A) What do you get when you multiply 12 by root 3 = 12√3
B)
What do you get when you multiply 5root3 by root3 = 5√9

so what now?:smile:



Original post by moththecat
That wont get me -5+4√3 what you said will get me 12-5√3


You need to divide the responses you gave in the first quote by 3. NOT root3
Reply 12
Original post by TenOfThem
Presumably you are unaware that full solutions are against the forum guidelines

I was unaware of this. Thanks for telling me! :smile:

Quick Reply