If f(x,y)=x2+20y2f(x,y) = x^2 + 20y^2f(x,y)=x2+20y2, what is nablaf\\nabla fnablaf?
langle2x,20yrangle\\langle 2x, 20y \\ranglelangle2x,20yrangle
langle2,40rangle\\langle 2, 40 \\ranglelangle2,40rangle
langle2x,40yrangle\\langle 2x, 40y \\ranglelangle2x,40yrangle
langlex,20yrangle\\langle x, 20y \\ranglelanglex,20yrangle