Differentiation

1. A curve is defined by the parametric eq. x(1+t)^2 & y=(1-t)^2
a. Find dy/dx in terms of t
b. Find the point on the curve at which the gradient is 0
c. Find also the gradient of the tangent to the curve at the point where x=y

2a. If 1/(1-x^2) = A/(1+x) + B/(1-x) is an identity, find the values of the
constants A & B
b. If f(x) = 1/(1-x^2), find f"(0) & f'"(0)
c. What is the value of f^n (0)