Compute the directional derivatives of the following functions along unit vectors at the indicated points in directions parallel to the given vector.
(a) $f(x, y) = x^y$, $(x_0, y_0) = (e, e)$, $d = 3i + 4j$
$\frac{7e}{5}$
(b) $f(x, y, z) = e^x + yz$, $(x_0, y_0, z_0) = (1, 1, 1)$, $d = (1, -4, 4)$
(c) $f(x, y, z) = xyz$, $(x_0, y_0, z_0) = (1, 0, 1)$, $d = (1, 0, -1)$
0
