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Surds help

Hi

Can anyone help with the following:

(2+√2)(3+√5)(√5-2)
(√5-1)(1+√2)

I have managed to get to the following but not sure what to do from here:

2√5 – 2 + √10 + √50 - 6√2
√5 + √10 - 1 - √2

Thanks
Original post by Flutegirl02
Hi

Can anyone help with the following:

(2+√2)(3+√5)(√5-2)
(√5-1)(1+√2)

I have managed to get to the following but not sure what to do from here:

2√5 – 2 + √10 + √50 - 6√2
√5 + √10 - 1 - √2

Thanks


What is your objective? If it's to rationalise the denominator then just multiply your fraction by (5+1)(1−2)(5+1)(1−2)\displaystyle \frac{(\sqrt5+1)(1-\sqrt2)}{(\sqrt5+1)(1-\sqrt2)} before you expand the brackets.
(edited 7 years ago)
Reply 2
Avatar for Flutegirl02
Flutegirl02
OP
Thanks. Yeah it's rationalising. I'll have a go tomorrow.
Reply 3
Avatar for mik1a
mik1a
10
The trick is to keep the denominator factorised, at least until you have done the 'multiply top and bottom by this' trick.

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