PLEASE HELP! Compute the difference quotient: [(f(x)- f(a))/(x-a)]..

Question

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

Answer 1

[-1/x^2 +1/a^2] / (x-a)

[ x^2 - a^2 ]/ [x^2 a^2 (x-a)]

[(x+a)(x-a)] / [x^2 a^2 (x-a)]

(x+a)/x^2a^2

note for when you get to differentiation the limit of this as x-->a is
2x/x^4 = 2/x^3