seem to have a problem with basic differentiation:

Question: y = 1/(x^2 + 1)

At point x = 1, y = 1/2

Work:

(x^2+1)^-1

-1(X^2+1)^-2 (2x)

(-x^2-1)^-2 (2x)

(-(1)^2 - 1)^-2(2(1)

however, 1 - 1 = 0 and applying ^2 means you are dividing two by zero? where did I go wrong, thanks.