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Math Help - Differenciation

  1. #1
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    Differenciation

    Find the equation of the normal to the curve y= x(1-2x)1/2 at the point (-4,-12)

    y= x(1-2x)1/2
    dy/dx = 1/2 (1-2x)-1/2


    do i sub in -4 now? If so, am i getting the gradient of the normal or the curve itself?
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  2. #2
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    Re: Differenciation

    Your derivation is wrong. Use product rule
    d(uv)/dx = u dv/dx + v du/dx.
    the derivative comes out to be dy / dx = (1-3x)/(1-2x)^1/2
    Now get dy/dx at x = -4
    that is the slope of tangent at x = -4.
    Negative reciprocal of this slope will give us slope of normal to the curve at x = -4.
    Thus slope of normal would be -1/[dy/dx] = - (1-2x)^1/2 / (1-3x)
    Now you can proceed further
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