Friday, September 12, 2014

What is the first and second derivatives of x/(x-1)^2?

We have the function f(x) = x/(x - 1)^2 and we have to
find the first and the second derivatives.


f(x) = x/(x -
1)^2


=> f(x) = x*(x -
1)^-2


Use the product rule to calculate the first
derivative


f'(x) = x*(-2)(x - 1)^(-3) + (x -
1)^(-2)


=> -2x*(x - 1)^(-3) + (x -
1)^(-2)


=> -2x/(x - 1)^3 + 1/(x -
1)^2


Again use the product rule to calculate the second
derivative


f'(x) = -2x*(x - 1)^(-3) + (x -
1)^(-2)


f''(x) = (-2)[(x - 1)^(-3) + (-3)*x*(x - 1)^(-4) +
(-2)*(x - 1)^(-3)


=> -2/(x - 1)^3 + 6x/(x - 1)^4 -
2/(x - 1)^3


=> -4/(x - 1)^3 + 6x/(x -
1)^4


The first derivative is -2x/(x - 1)^3 +
1/(x - 1)^2 and the second derivative is -4/(x - 1)^3 + 6x/(x -
1)^4

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