Use algebra and the limit definition of the derivative to

find f′(−1), when

$\displaystyle

f(x) = \frac {2}{1 -5x}

$

I know the limit definition of the derivative is:

as the Lim h-->0 [F(x+a)-f(x)]/h

I get confused on the actual agebra part.

If anyone can kindly work it out, that would be very nice. thank you.