分类：教育/科学-升学入学-考研
问题：数学作业题目在附件中，谢谢！ 
题目在附件中，谢谢！
回答：解:2.f(x,y+h)=x^2-2x(y+h)+3(y+h)^2
f(x,y+h)-f(x,y)
=x^2-2x(y+h)+3(y+h)^2-(x^2-2xy+3y^2)
=x^2-2xy-2xh+3y^2+6hy+3h^2-x^2+2xy-3y^2
=-2xh+6hy+3h^2
[f(x,y+h)-f(x,y)]/h
=(-2xh+6hy+3h^2)/h
=-2x+6y+3h