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Surds

stuck on simplifying surds as fractions.

6√2 4√7
----- + -----
3+√7 √2-1

I think it involves rationalising the denominator, however when I do that i seem to get the wrong answer. Can someone break down how they would answer this question then I would understand it and see where i have went wrong.

Thanks.
Reply 1
Post some working, you have the right idea about rationalising the denominators.

Also try and use latex
62(3+7)+47(21)\frac{6\sqrt 2}{(3+\sqrt 7)} + \frac{4\sqrt 7}{(\sqrt2-1)}


I would probably tackle the fractions one at a time, so simplify the first one, then simplify the last one. PS my answer doesn't look too pretty so... it might be wrong?

Start with

62(3+7)\frac{6\sqrt 2}{(3+\sqrt 7)}

To rationalise the denominator, we must multiply everything by

(37){(3-\sqrt 7)} ... see below:



(62)(37)(3+7)(37)\frac{(6\sqrt 2)(3-\sqrt 7)}{(3+\sqrt 7)(3-\sqrt 7)}

=18261497=\frac{18\sqrt 2 - 6\sqrt 14}{9-7}

=92314=9\sqrt 2 - 3\sqrt 14

Can you do the rest?
Reply 3
Chelle-belle
62(3+7)+47(21)\frac{6\sqrt 2}{(3+\sqrt 7)} + \frac{4\sqrt 7}{(\sqrt2-1)}


I would probably tackle the fractions one at a time, so simplify the first one, then simplify the last one. PS my answer doesn't look too pretty so... it might be wrong?

Start with

62(3+7)\frac{6\sqrt 2}{(3+\sqrt 7)}

To rationalise the denominator, we must multiply everything by

(37){(3-\sqrt 7)} ... see below:



(62)(37)(3+7)(37)\frac{(6\sqrt 2)(3-\sqrt 7)}{(3+\sqrt 7)(3-\sqrt 7)}

=18261497=\frac{18\sqrt 2 - 6\sqrt 14}{9-7}

=92314=9\sqrt 2 - 3\sqrt 14

Can you do the rest?


That is how I worked it out but the book answer says √14+4√7+9√2 actually wait I see where I messed up
stefl14
That is how I worked it out but the book answer says √14+4√7+9√2 actually wait I see where I messed up

Hope you got it :smile:

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