Given a function f(@) = f(21, 12) = 202 +2143 -2142, where = [:1, 12]TER?. (a) Find the gradient vector Vf(x) and the Hessian matrix V? f(x) of f(x). (b) Show that V'f(2, ) is positive definite by definition. (c) Show that V2f(2, =) is negative definite by the leading principal minor test. (d) Show that V2f(1, 0) is indefinite by the eigenvalue test