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    Need help please


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    (Original post by z_o_e)

    Need help please


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    For part (a):

    27^{-\frac{2}{3}} = \frac{1}{27^{2/3}}

    For part (b):

    You need to rationalise the denominator.
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    (Original post by SherlockHolmes)
    For part (a):

    27^{-\frac{2}{3}} = \frac{1}{27^{2/3}}

    For part (b):

    You need to rationalise the denominator.
    Got the first bit

    Is it like this?
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    Rationalising the denominator means making it a rational number (obvious, I know ) by multiplying it with what you did in the picture, it would still leave you with an irrational number on the bottom of the fraction.

    To rationalise a square root, you multiply it by itself.

    So to rationalise Root 2, you multiply it by root 2 which gives you 2. This is just one of the laws of indices which you should know. (Don't forget to multiply the top AND the bottom by root 2)

    It will leave you with a fraction but once you simply everything, you should no longer be left with a fraction.
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    (Original post by JaredzzC)
    Rationalising the denominator means making it a rational number (obvious, I know )

    To rationalise a square root, you multiply it by itself.

    So to rationalise Root 2, you multiply it by root 2 which gives you 2. This is just one of the laws of indices which you should know. (Don't forget to multiply the top AND the bottom by root 2)

    It will leave you with a fraction but once you simply everything, you should no longer be left with a fraction.
    This?
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    (Original post by z_o_e)
    Got the first bit

    Is it like this?

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    The denominator is still not a rational number if you do that. You want to multiply numerator and denominator by \sqrt{2}.
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    Almost! root 2 x root 18 = root 36.
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    (Original post by JaredzzC)
    Almost! root 2 x root 18 = root 36.
    Yeppp whats the next step x


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    (Original post by z_o_e)
    Got the first bit

    Is it like this?
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    For part (a) you should probably simplify 1/27^2/3 more as well because 27 has an integer cube root
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    (Original post by z_o_e)
    Yeppp whats the next step x


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    now you need to get root 36 into (something multiplied by root 2) and then you can divide through by 2 to get rid of the fraction
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    (Original post by JaredzzC)
    now you need to get root 36 into (something multiplied by root 2) and then you can divide through by 2 to get rid of the fraction
    I dont understand


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    (Original post by z_o_e)
    Got the first bit

    Is it like this?
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    Posted from TSR Mobile
    Rationalizing radical denominator means to multiply the numerator and denominator by the same radical.

    For example

     \dfrac{5}{\sqrt{3}} = \dfrac{\sqrt{3} \times 5}{\sqrt{3} \times  \sqrt{3}}
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    (Original post by z_o_e)
    I dont understand


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    Ignore that.

    \sqrt{36} = ...

    ?
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    (Original post by z_o_e)
    I dont understand


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    I think you need to revise your laws of indices for surds (this is what the question is testing you on)

    If you look at the attachment, it shows how you can break up surds to get it into a different from.
    This is what you'll need to do to the root 36 to try get b(root2)

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    (Original post by notnek)
    Ignore that.

    \sqrt{36} = ...

    ?
    6


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    Correct. So what do you have now? Post your working.
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    (Original post by JaredzzC)
    I think you need to revise your laws of indices for surds (this is what the question is testing you on)

    If you look at the attachment, it shows how you can break up surds to get it into a different from.
    This is what you'll need to do to the root 36 to try get b(root2)
    No need in this case. 36 is a square number
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    (Original post by notnek)
    No need in this case. 36 is a square number
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    8 cancels to 4 and


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    (Original post by notnek)
    No need in this case. 36 is a square number
    However the question is asking here to leave it in the form a+b\sqrt{2} = ...

    Oh wait, ignore me, you're right

    Was not reading the steps correctly.
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    (Original post by z_o_e)
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    8 cancels to 4 and


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    Now you divide each part of the top fraction by 2 which will get rid of the 2 on the bottom of the fraction and voila, you have your answer!

    For 8\sqrt{2} , you just divide the 8 by 2 and keep the \sqrt{2} as it is.
 
 
 
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