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    Could someone help me with this question, I know the answer and you get the answer. But I don't understand how to get the answer properly.
    Question; (3+15)2(Squared)

    Give your answer in the form n+m/5 where n and m are integers. Toal 4 marks.
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    (Original post by SBizzy)
    Could someone help me with this question, I know the answer and you get the answer. But I don't understand how to get the answer properly.
    Question; (3+15)2(Squared)

    Give your answer in the form n+m/5 where n and m are integers. Toal 4 marks.
    Can you put a picture of the original question please?
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    Can u post a picture of the question or clarify how u have written the question?
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    (Original post by atsruser)
    Can you put a picture of the original question please?
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    (Original post by Shaanv)
    Can u post a picture of the question or clarify how u have written the question?
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    Expand using the binomial theorem. You will be left with two numbers 3 and 15 their sum will be n. For m you are left with 2sqrt(15*3), which is sqrt(45) which is equal to sqrt(3^2*5).The root of 3^2 is 3. You are done.
    P.S. 45=15*3 in case you were wondering where the 45 came from.
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    (Original post by SBizzy)
    Could someone help me with this question, I know the answer and you get the answer. But I don't understand how to get the answer properly.
    Question; (3+15)2(Squared)

    Give your answer in the form n+m/5 where n and m are integers. Toal 4 marks.
    What have you tried?

    Hint:
    \sqrt{15}=\sqrt{3}\sqrt{5}

    \therefore (\sqrt{3}+\sqrt{15})^2=3(1+\sqrt  {5})^2
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    (Original post by Moriheru)
    Expand using the binomial theorem. You will be left with two numbers 9 and 15 their sum will be n. For m you are left with 2sqrt(15*3), which is sqrt(45) which is equal to sqrt(3^2*5).The root of 3^2 is 3. You are done.
    P.S. 45=15*3 in case you were wondering where the 45 came from.
    Binomial theorum is unnecessary for this level of question.
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    (Original post by AmmarTa)
    Binomial theorum is unnecessary for this level of question.
    That is simply what is called multiplying out brackets(at least in this case).... I just multiplied brackets out, which I believe is also using the binomial theorem technically even though you don't calculate coefficients with factorials etc.
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    (Original post by Moriheru)
    That is simply what is called multiplying out brackets(at least in this case).... I just multiplied brackets out, which I believe is also using the binomial theorem technically even though you don't calculate coefficients with factorials etc.
    Technically but this is a GCSE level question (I assume) so I wouldn't try to over complicate the maths and make it harder for the OP to understand :P
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    (Original post by AmmarTa)
    Technically but this is a GCSE level question (I assume) so I wouldn't try to over complicate the maths and make it harder for the OP to understand :P
    Yes ofc I just seriously thought that using the binomial theorem is what you called the simple procedure...
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    (Original post by Kambu)
    This is how i expect they want you to do it. Multiply out the brackets and realise that root 45 can be broken down into two seperate roots... one of which is root 9...which is just 3. So it all works out nicely

    Attachment 697934
    Thank you very much!!!!!!!!!!
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    (Original post by Moriheru)
    Expand using the binomial theorem. You will be left with two numbers 3 and 15 their sum will be n. For m you are left with 2sqrt(15*3), which is sqrt(45) which is equal to sqrt(3^2*5).The root of 3^2 is 3. You are done.
    P.S. 45=15*3 in case you were wondering where the 45 came from.
    Binomial isn't needed for this question. You would be overcomplicating the problem too much.

    (Original post by Kambu)
    This is how i expect they want you to do it. Multiply out the brackets and realise that root 45 can be broken down into two seperate roots... one of which is root 9...which is just 3. So it all works out nicely
    You aren't meant to post the entire answers. Please read the rules. You are meant to guide them step by step.
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    (Original post by SBizzy)
    Could someone help me with this question, I know the answer and you get the answer. But I don't understand how to get the answer properly.
    Question; (3+15)2(Squared)

    Give your answer in the form n+m/5 where n and m are integers. Toal 4 marks.
     (a+b)^2 = (a+b)(a+b) = a^2+2ab+b^2 by distributing.

    This is something you should remember; squaring a bracket with two terms results in the the first term squared + 2 times the product of the terms + the other term squared.
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    (Original post by SBizzy)
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    What would you do to rationalise this?

    Take this example. If I have \frac 2\sqrt 2 I would multiply it by \frac{\sqrt2}{\sqrt{2}} to get \frac{2\sqrt2}{2} which simplifies to \sqrt 2
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    (Original post by SBizzy)
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    You would use difference of two squares for the numerator:

    (a+b)(a-b) = a^2 - b^2

    You can substitute the numbers into a and b and simplify like I have done above.

    Then you can rationalise the denominator by multiplying both the numerator and denominator by the square root of 31, and simplifying the fraction if possible.
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    Surds are so annoying, could someone help with this question. show that (3-/12)2 = 21 - 12/3
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    (Original post by SBizzy)
    Surds are so annoying, could someone help with this question. show that (3-/12)2 = 21 - 12/3
    Er... not sure what that thing is supposed to mean... please make it clearer!
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    (Original post by SBizzy)
    Surds are so annoying, could someone help with this question. show that (3-/12)2 = 21 - 12/3
    1. What did you think of the help provided to your previous surds question? Did you complete it in the end? Is there anything you can learn from it?

    2. Your question seems to be missing the surds.

    3. Where is your attempt at this question? It is fine to be completely stumped but to say nothing at all with no working is not.
 
 
 
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