Math Is Fun Forum

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Surds

I'm not getting the answer that I have been given for this one.. but I can't see where I have gone wrong. Can anyone help?

Write this surd in it's simplest form:

Thanks

Last edited by Daniel123 (2007-08-08 07:11:06)

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Surds

That's correct.

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

yonski

Member

Registered: 2005-12-14

Posts: 67

Re: Surds

Best when you have fractional surds to get rid of the surd in the denominator. You can do this in this case by multiplying top and bottom by root 3. So we have

Answer = (1/3)√8√3 + √24 + √294
           = (1/3)√4√6 + √4√6 + √49√6
           = (2/3)√6 + 9√6
           = (29/3)√6

...which is what you have, and that's as simplified as it gets. The key thing here is to spot the common surd and collect up all the terms. Your method seems a bit too long-winded and unecessarily fiddly. You did have the right answer though, which is the important thing, just try not to over-complicate it all.

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Student: "What's a corollary?"
Lecturer: "What's a corollary? It's like when a theorem has a child. And names it corollary."

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Surds

What answer were you given? Is it the same value in a different form?

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Why did the vector cross the road?
It wanted to be normal.

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: Surds

The question had multiple choice answers, and none of them are that close to my answer... :s. I thought I had it right