Exercise 7.1.1. Show, directly from the definition, that the function f : R2 - R2 defined by f (x1, x2) = (x1 - x2, 2x1*2) is differentiable (on all of R-) and compute its derivative at each point. At which points c does the derivative Df(c) fail to be invertible?Exercise 7.2.2. Suppose f : IRS -> R2 is differentiable at 0) and 0 2 Df (0) = 3 2 Find the directional derivative in the direction of the vector