Please help.Let

f(x,y)=x^(2)y-3xy^(3)

\ a. Find

gradf

\ b. Find the directional derivative of

f

in the direction of

(:1,4:)

at the point

(-1,2)

\ c. Find the direction of maximum change for

f

at the point

(-1,2)

5. Let f(x,y)=x2y3xy3 a. Find f b. Find the directional derivative of f in the direction of 1,4 at the point (1,2) c. Find the direction of maximum change for f at the point (1,2)