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    (Original post by NiamhM1801)
    And I thought that √9 could be 3 or -3? As (-3)² is 9?
    This is a common source of confusion for students, teachers and even textbooks.

    This explains things.
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    (Original post by Ano123)
    Hi, I need help on a particularly awkward question.
    The question is :

    Simplify fully the expression

     \displaystyle \frac{3x^3}{x^2} \times \sqrt{\frac{9}{x^2}} .
    I get an answer but it's just cant be right.
    Could someone quickly just post an answer so I can see if I'm right?
    Thank you!
    Call it f(x), then:

    \displaystyle f(x) = \begin{cases} 9 \, & \text{for } x > 0 \\ -9 \, &\text{for } x < 0
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    (Original post by Ano123)
    Hi, I need help on a particularly awkward question.
    The question is :

    Simplify fully the expression

     \displaystyle \frac{3x^3}{x^2} \times \sqrt{\frac{9}{x^2}} .
    I get an answer but it's just cant be right.
    Could someone quickly just post an answer so I can see if I'm right?
    Thank you!
    Where did you get this question from? Textbook? Past paper?
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    (Original post by notnek)
    Where did you get this question from? Textbook? Past paper?
    Just made it up.
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    Wtf you're getting an extra GCSE for this **** which the IGCSE tests you on.
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    (Original post by Ano123)
    Just made it up.
    OK - I doubt that it would be in a FM GCSE paper.
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    (Original post by _Xenon_)
    Wtf you're getting an extra GCSE for this **** which the IGCSE tests you on.
    AQA FM is a much harder than IGCSE (CIE and Edexcel).
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    (Original post by notnek)
    AQA FM is a much harder than IGCSE (CIE and Edexcel).
    I have never seen an IGCSE paper, but tbh looking at the specification there is a fair amount of overlap with the AQA FM course, and some stuff on it that i don't recall being on the fm course but it all comes down to how hard the questions are tbh
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    (Original post by samb1234)
    I have never seen an IGCSE paper, but tbh looking at the specification there is a fair amount of overlap with the AQA FM course, and some stuff on it that i don't recall being on the fm course but it all comes down to how hard the questions are tbh
    There is some overlap but the difficulty of the questions in AQA FM are in a different league.
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    (Original post by notnek)
    There is some overlap but the difficulty of the questions in AQA FM are in a different league.
    I'll take your word for it, I did AQA FM and GCSE too long ago to really be able to tell how difficult they are anymore
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    (Original post by notnek)
    There is some overlap but the difficulty of the questions in AQA FM are in a different league.
    Yep IGCSE are many many times tougher questions, I agree.
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    (Original post by _Xenon_)
    Yep IGCSE are many many times tougher questions, I agree.
    I think most of the people taking FM would wish this was true
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    (Original post by notnek)
    I think most of the people taking FM would wish this was true
    FM A level?
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    (Original post by _Xenon_)
    FM A level?
    No. AQA Level 2 Further Maths. Which is what this thread is about.
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    (Original post by notnek)
    No. AQA Level 2 Further Maths. Which is what this thread is about.
    But can you please help me with differentiation? :-)
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    (Original post by _Xenon_)
    But can you please help me with differentiation? :-)
    Not here. Ask in the maths forum.
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    (Original post by notnek)
    Not here. Ask in the maths forum.
    OK but please reply OK?

    Thanks
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    (Original post by Ano123)
    Not quite.  \sqrt 9 = 3 .
     \sqrt 9 \neq -3 .
    What's actually happening here is you made a mistake when square rooting [/tex] x^2 [/tex]. If you put any negative number as x into the expression, say -1 you get  \sqrt {(-1)^2} = \sqrt 1 = 1 . So as you can see if x is a negative number then it returns a positive number.
    So actually  \sqrt {x^2} = | x | .
    The vertical lines mean the absolute value. Meaning we just take the magnitude of the number. So |-2| = 2.
    |-100|=100 etc.
    So, the answer to the original question is 9 and -9?
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    (Original post by Ishan_2000)
    So, the answer to the original question is 9 and -9?
    Yes it is -9 for x<0 and 9 for x>0. You can't just say 9 and -9 without stating when it is one or the other,
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    (Original post by Ishan_2000)
    So, the answer to the original question is 9 and -9?
    What was the original question?
 
 
 
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