df dt t=-1 (a) Consider the function f(x, y) = xy+y. Suppose that x=1+t2 and y = 2t. Use an appropriate chain rule for a function of several variables to calculate (b) Consider the function f(x, y) = ry. Suppose that x=s+t and y appropriate chain rule for a function of several variables to calculate s22t. Use an of af ds and t