differentiation + L Hopital's Rule 的问题

ratloverice

我那天在做习题时找到这几道题目，想了很久都不会做
麻烦大家教教我

1. Use the definition of the derivative of  f(x),

  lim      ( f (x+h) - f (x) ) / h

  x->0  

to obtain f ' (x) for f (x)  7 / ( 5(x^3) - 11 )^1/2

2. Find the derivative of y with respect to x. Simplify your answers.

(a) y = ( 2 / (x)^4/5 - x^3 ) ( 1 - 2 (7x)^1/5 )^1/2

(b) y = ( csc^2 (x)^1/2 - (x)^1/4 )^1/2

(c) cos(xy) = 1 - x^2

3. Use L Hopital's Rule to evaluate the following limits.

(a) lim            ( ( 2 cosx / sin 2x ) - 1/x )

     x-> 0^+

麻烦帮帮我

好难