2.作适当的变量变换求解下列方程:-|||-(1) dfrac (dy)(dx)=((x+y))^2 ;-|||-(2) dfrac (dy)(dx)=dfrac (1)({(x+y))^2} ;-|||-(3) dfrac (dy)(dx)=dfrac (2x-y+1)(x-2y+1) ;-|||-(4) dfrac (dy)(dx)=dfrac (x-y+5)(x-y-2) :-|||-(5) dfrac (dy)(dx)=((x+1))^2+((4y+1))^2+8xy+1 ;-|||-(6) dfrac (dy')(dx)=dfrac ({y)^6-2(x)^2}(2x{y)^5+(x)^2(y)^2} :-|||-(7) dfrac (dy)(dx)=dfrac (2{x)^3+3x(y)^2+x}(3{x)^2y+2(y)^3-y} .