Find the directions in which the function increases and decreases most rapidly at Po Then find the derivatives of the function in these directions f x y z x y yz Po 1 1 4 5 27 j The direction in which the given function f x y z x y yz increases most rapidly at Po 1 1 4 is u 27 Type exact answers using radicals as needed The direction in which the given function f x y z x y yz decreases most rapidly at Po 1 1 4 is v k Type exact answers using radicals as needed 27