求解z=2x+3y^2则dz=多少?a,2dx+3y^2dy b.2dx+6ydy c.2xdx+6ydy d.2xdx+3y^2dy应选()

问题描述:

求解z=2x+3y^2则dz=多少?
a,2dx+3y^2dy b.2dx+6ydy c.2xdx+6ydy d.2xdx+3y^2dy
应选()