Calculate the directional derivative

Calculate the directional derivative of f (x,y)=x^2y^3 in the direction of v=3i+j at the point P=(-2,-1). Remember to normalize the direction vector.

Du f(-2,-1)=?

grad f = (2xy^3,3x^2y^2) = (4,12).

Directional derivative = grad f * v/||v|| = (4,12)*(3,1)/sqrt(10) = 24/sqrt(10).