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Math Help - Stuck finding the derivative of x^2 using difference quotient

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    Stuck finding the derivative of x^2 using difference quotient

    Hey id be greatful to anyone who can help me with this which i guess is easy but im too dumb to get...

    Whilst finding the derivative of x2 (using the difference quotient) it is at this step that i get confused and need help on...

    f'(x)= (x+dx)2-(x)2/dx

    how do they get from the above equation to......

    x2+2xdx+(dx2)-(x)2/dx

    any explanation of this would be great, cheers
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    Re: Stuck finding the derivative of x^2 using difference quotient

    Quote Originally Posted by fwp0406 View Post
    Hey id be greatful to anyone who can help me with this which i guess is easy but im too dumb to get...

    Whilst finding the derivative of x2 (using the difference quotient) it is at this step that i get confused and need help on...

    f'(x)= (x+dx)2-(x)2/dx

    how do they get from the above equation to......

    x2+2xdx+(dx2)-(x)2/dx

    any explanation of this would be great, cheers
    Expand the brackets.
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    Re: Stuck finding the derivative of x^2 using difference quotient

    (a+ b)^2= a^2+ 2ab+ b^2 so that (x+ dx)^2= x^2+ 2(x)(dx)+ (dx)^2.
    Last edited by HallsofIvy; July 26th 2012 at 10:53 AM.
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