Given the function f(x) = 12x-3x + 4. (a) use the sign diagram of f (x) to find write the intervals where the function increases and decreases, and the minimum and or muximum point((-s) and values (b) find the greatert and the least value of the function on the segment -1,4 (c) use f" (x) to find the inflection points The funtion of two variables z = f(x, y) is given by f(x, y) = sin(y-4x) + 3y 1-8x. Find all second order purtial derivatives of the function