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    Hi help me dudes! :confused:

    I am rather confused with the whole concept of GCSE mathematics, expanding brackets with Surds. For instance, one of the questions I find very difficult is:

    Expand the brackets then and then simplify:

    (√2-3)(√2+7)

    Basically, I ca expand the expression but somehow cannot simlify it. :confused:

    Please give me your thoughts into how I can resolve my problem with Surd Expansion.

    Cheers
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    Show us what you got when you expanded it.
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    what have you got to?
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    ok when I expanded it I got √4√4 +7√2 -3√2 -21
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    just expand it as 2 normal brakets. so (a+b)(c+d)= ac+ad+bc+bd and then simplify by adding any of the terms which are numbers or surds of the same root together.
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    (Original post by PhyMath)
    Show us what you got when you expanded it.

    ok when I expanded it I got √4√4 +7√2 -3√2 -21

    I used the "FOIL" method to expand
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    Where does \sqrt{4}\times \sqrt{4} come from?

    Now collect like terms
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    (Original post by Danules)
    just expand it as 2 normal brakets. so (a+b)(c+d)= ac+ad+bc+bd and then simplify by adding any of the terms which are numbers or surds of the same root together.
    Ok thanks

    So it would simlify into:

    -17+5√2

    ???
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    (Original post by Sophie Maywood)
    Ok thanks

    So it would simlify into:

    -17+5√2

    ???
    No, be careful collecting terms
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    now you've expanded, simplify. so root 4 times root 4 is 4 as the root cancel out. 4-21= -17. 7lot of root 2 and - 3 lots of root 2 is like 7x-3x except x is root 2. so there are 4 root 2's. So simplified it is 4 lots of root2- 17.
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    What do you get when you times two of the same roots... Think about it.
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    So in theory, if you simplify a surd, then the number inside the root needs to be as small as possible and the number outside the surd needs to be the largest square number?

    e.g

    √48 = 4√3
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    √2 x √2 = 2
 
 
 
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Updated: November 25, 2008

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