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Thread: One calculus questions

  1. #1 One calculus questions 
    Forum Freshman FancyShoes's Avatar
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    Just one question I did not understand on my calculus worksheet.

    If y= 3/4+x^2 then dy/dx = ?

    3/2x?


    whats the interval of 1/mower? lnmower... heh
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  3. #2  
    Forum Professor river_rat's Avatar
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    Hey fancy shoers

    That looks like a typo to me - the question should read

    If y= 3/4*x^2 then dy/dx = ?


    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  4. #3  
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    Well IF Y = 0.75 X^2 then dy/dx= 1.5x which is the same.

    Rare for me to post in maths, but I'll make an exception, I agree with RR.
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  5. #4  
    Forum Freshman FancyShoes's Avatar
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    its actually this. sorry i did not put brackets if y=3/(4+x^2) then dy/dx = ?
    whats the interval of 1/mower? lnmower... heh
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  6. #5  
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    Quote Originally Posted by FancyShoes
    its actually this. sorry i did not put brackets if y=3/(4+x^2) then dy/dx = ?
    Set z = 4 + x<sup>2</sup>. What is dz/dx? Show you are trying, even if its wrong
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  7. #6  
    Forum Professor river_rat's Avatar
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    Ah use the quotient rule or the chain rule - what ever you feel more comfortable with really. Your answer is definitely not correct btw.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  8. #7  
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    differentiate it from first principles (if you are not yet familiar with Quotient/chain) - it'll be good practice anyway.

    let's say f(x) = 1/(5x+3)

    I wrote that one out on paper, I don't know where all the maths symbols are but I got

    dy/dx = -5/(5x+3)^2

    River rat will tell if I've made a balls up.....

    It looks like homework though, so you'll have to do it yourself,
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  9. #8  
    Forum Professor river_rat's Avatar
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    Looks fine to me Megabrain - though doing the original question by first principles looks very hairy!
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  10. #9  
    Forum Freshman FancyShoes's Avatar
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    ya I went and asked my teacher answer was 6x/(4+x^2)^2 if anyone wanted to know. Ya he told me to use the chain rule
    whats the interval of 1/mower? lnmower... heh
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  11. #10  
    Forum Professor river_rat's Avatar
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    Quote Originally Posted by FancyShoes
    ya I went and asked my teacher answer was 6x/(4+x^2)^2 if anyone wanted to know. Ya he told me to use the chain rule
    I hope he did not say that 6x/(4+x^2)^2 was the answer! Eish.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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