Plot3D[-x^2-2x y +6y , {x,-10,10}, {y,-10,10}, PlotRange -> {{-10,10}, {-10,10},{-30,30}}]

ContourPlot[x y^2+y, {x, -3,3}, {y,-3,3},ContourShading->None, GridLines->Automatic, Contours -> {-5,-4,-3,-2,-1,0,1,2,3,4,5},BaseStyle->{FontSize->12}, ContourStyle->Directive[{Blue, Thick}],ContourLabels->Function[{x,y,z},Text[z,{x,y},Background->White]]]

Plot[4x+2, {x,-10,10}]

Plot[2y^2+y, {y,-10,10}]

Plot3D[3x y+3y^2/2+2x^3 , {x,-5,5}, {y,-5,5}, PlotRange -> {{-5,5}, {-5,5},{-2,2}}]