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Maths C1 Help

Hi, I'm stuck on a C1 question on surds and would appreciate any help :smile:.

Express
2√2 / √3-1 - 2√3 / √2 +1

in the form of p √6 + q√3 + r√2 where the integers p, q and r are to be found.

Please note: the √3-1 covers the whole denominator for that fraction

So far I've gotten P = 2√6
Q = 2√3
but I cannot find what R is equal to.

Thanks for your time.
(edited 10 years ago)
Reply 1
I got different answer then you.

First i multiplied 2√2 / √3-1 by √3+1 / √3+1 and simplified to get √6 +√2
and then i multiplied 2√3 / √2 +1 by √2-1 / √2-1 and simplified to get 2√6 -2√3
then did (√6 +√2) - (2√6 -2√3)

and i got -√6 + 2√3 +√2

so P = -1 Q = 2 R = 1

(I am not entirely sure of my answers)
Reply 2
Original post by ChemEng
I got different answer then you.

First i multiplied 2√2 / √3-1 by √3+1 / √3+1 and simplified to get √6 +√2
and then i multiplied 2√3 / √2 +1 by √2-1 / √2-1 and simplified to get 2√6 -2√3
then did (√6 +√2) - (2√6 -2√3)

and i got -√6 + 2√3 +√2

so P = -1 Q = 2 R = 1

(I am not entirely sure of my answers)


I done the question again and I got -1, +1 and -2 and it's in that order. On my sheet there was a printing error so √3-1 was all covered by the root which is why my original answers were way off.
(edited 10 years ago)
Reply 3
Original post by ChemEng
I got different answer then you.

First i multiplied 2√2 / √3-1 by √3+1 / √3+1 and simplified to get √6 +√2
and then i multiplied 2√3 / √2 +1 by √2-1 / √2-1 and simplified to get 2√6 -2√3
then did (√6 +√2) - (2√6 -2√3)

and i got -√6 + 2√3 +√2

so P = -1 Q = 2 R = 1

(I am not entirely sure of my answers)


2√2 / √3-1 by √3+1 / √3+1 and simplified to get √6 +√2

How did you simplify that ^^ to √6 +√2
Reply 4
Original post by adam1233
I done the question again and I got -1, +1 and -2 and it's in that order


I just did it again and i got the same answers.
Maybe your making a mistake at this point:
(√6 +√2) - (2√6 -2√3)
Maybe your forgetting the minus between the brackets
you should get:
√6 +√2 -2√6 +2√3
which equals to -√6 + 2√3 +√2
Original post by ChemEng
I got different answer then you.

First i multiplied 2√2 / √3-1 by √3+1 / √3+1 and simplified to get √6 +√2
and then i multiplied 2√3 / √2 +1 by √2-1 / √2-1 and simplified to get 2√6 -2√3
then did (√6 +√2) - (2√6 -2√3)

and i got -√6 + 2√3 +√2

so P = -1 Q = 2 R = 1

(I am not entirely sure of my answers)


I got the same answers as you and also worked it out with the same method so I think it's fair to say that we're right :smile:
Reply 6
Original post by MsFahima
2√2 / √3-1 by √3+1 / √3+1 and simplified to get √6 +√2

How did you simplify that ^^ to √6 +√2


for the numerator i got 2√6 + 2√2
and for the denominator i got 2
and then simplified to √6 +√2
Reply 7
Original post by ChemEng
I just did it again and i got the same answers.
Maybe your making a mistake at this point:
(√6 +√2) - (2√6 -2√3)
Maybe your forgetting the minus between the brackets
you should get:
√6 +√2 -2√6 +2√3
which equals to -√6 + 2√3 +√2

Ah yes, thank you.
Reply 8
Original post by ChemEng
for the numerator i got 2√6 + 2√2
and for the denominator i got 2
and then simplified to √6 +√2


Yeah, I got that now. Thanks :biggrin:
How far are people with the syllabus ?


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