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    I've got the question:

    y=4/x^2 at x=-1

    I would be able to do it, but the fraction threw me off. Little help please?
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    y = 4*x^-2
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    \frac{4}{x^2} = 4x^{-2} (Remember that x^{-n} = \frac{1}{x^n} )
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      (Original post by JoshCoulthard)
      I've got the question:

      y=4/x^2 at x=-1

      I would be able to do it, but the fraction threw me off. Little help please?
      y= 4/x^2 is the same thing as y=4x^-2

      First find the coordinate of the point (sub x = -1 into the equation to find y)
      Then dy/dx to find the gradient.
      Then use y-y1=m(x-x1) to find the equation.
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      (Original post by im so academic)
      Remember that you are asked to find the tangent, so it's -1/m.
      I'm afraid you're wrong there. If m is the value of dy/dx at the point with x=-1 then -1/m will give you the gradient of the normal to the curve at that point and not the tangent.
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      (Original post by Farhan.Hanif93)
      I'm afraid you're wrong there. If m is the value of dy/dx at the point with x=-1 then -1/m will give you the gradient of the normal to the curve at that point and not the tangent.
      Beat me to it lol
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      Yeah you just fling the bottom part of the fraction to the top (which means it's now multiplying the top number) and change the symbol of the power.
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      (Original post by im so academic)
      y= 4/x^2 is the same thing as y=4x^-2

      First find the coordinate of the point (sub x = -1 into the equation to find y)
      Then dy/dx to find the gradient. Remember that you are asked to find the tangent, so it's -1/m.
      Then use y-y1=m(x-x1) to find the equation.
      How academic of you.
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        (Original post by Farhan.Hanif93)
        I'm afraid you're wrong there. If m is the value of dy/dx at the point with x=-1 then -1/m will give you the gradient of the normal to the curve at that point and not the tangent.
        Damn it, I knew you didn't have to do the -1/m thing, but never mind. :sad:

        Tangent = don't edit gradient
        Normal/perpendicular = edit gradient

        Utter fail. Thank you though.

        :getmecoat:
       
       
       
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