Let f(x) = (x-1) / (x+1) for all x is not equal to -1. Then f'(1) equals...?

Question

Please show me how to reach the answer as well, thank you.

Answer 1

By quotient rule:-
f ` (x) = ((x + 1) - (x - 1)) / (x + 1)²
f ` (x) = 2 / (x + 1)²
f ` (1) = 1 / 2

Answer 2

Use the quotient rule:

f'(x) = [(x+1) - (x-1)] / (x+1)^2 = 2 / (x+1)^2

Answer 3

use the quotient rule

f'(x)= [ (x+1)(1)-(x-1)(1) ] / (x+1)^2 = 2/(x+1)^2

so f'(1)= 2/(1+1)^2 = 2/4 = 1/2 = .5