Problem 2 (a) 6 Real Points; b) 7 Real Points) a) Find the approximation of the function derivatives fxxx(x, y) =? Use the forward difference formula for the 1st derivative, backward for the 2nd, and central formula for the 3rd derivative. Use the notations: f(x, y) = f(x, y) = fi j f(x+h, y) = f (xi+1, yj) = fi+₁j, f(x+h, y + k) = = f (xx+1, j+1) = fi+1 j+1, where x₁ = x, x₁+₁ = x + h; y; = y, and yj+₁ = y +k. b) Find the truncation error of the formula 1 k2 − (fij) = (fi j+1 - 2fi j + fi j−1) ?