x+y+1=0 suy ra x+y=1
Làm câu A nhé B,C tương tự
A= x^2.(x+y-2)-(xy+y^2-2y)+(y+x-1)=0-y.(x+y-2)+1=1
Hok tốt
sory, chưa lại
x+y=-1
\(A=x^2.\left(x+y\right)-y^2.\left(x+y\right)+x^2+2x+2y+3\)
\(A=x^2.\left(-1\right)-y^2.\left(-1\right)+x^2+2x+2y+3\)
\(A=-x^2+y^2+x^2+2\left(x+y\right)+3=y^2-2+3=y^2+1\)
????