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    Can some please tell me how to work out the following question please. :o:

    Find the range of values of x for which the gradient of the curve y = x^4 − 2x^2 is negative.
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    Differentiate it and find the set of values of x such that  \dfrac{dy}{dx} < 0 .

    Remember that, to differentiate a term of the form  x^n , then  \dfrac{d}{dx} (x^n) = nx^{n-1} - multiply by the power and take away one from the power.
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    gradient= 4x^3-4x
    4x(x^2-1)<0
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    differentiate the function then investigate which parts of the differentiated function are positive and negative by setting y'=0 to see where in crosses the x axis...
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    Thankyou very much.
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    Okay I differentiated it and got got three different values of x, 1, and the square root of 1 and minus the square root of 1 and also found the y co-ordinates of these points. How exactly would I write this as an answer though knowing where to put the < and > signs. I was never very good at that. :o:
 
 
 

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