Question

Finishing my derivative Q.
If I need to compelete a table I would use
−x^−2(dx)
to find dy? example if x=4 and dx = 1.000 then I have
−4^−2(1.000)
=-.0625? and if my dx=delta(x) And use f(x+dx)-f(x) which would be
4^−1+1.000−4^−1=1.000
for delta y?