Find the second-order Taylor formula for f(x, y) = (7x + 6y) at xo = (0, 0). Note that R2 (0, h) = 0 in this case. (Use symbolic notation and fractions where needed. Give your answer in the form of f (h . h2) = f(1, m) where I = h, and m = h2.) f(l, m) =