\(a,A+B=x^2-2x-y^2-1+\left(-2x\right)^2+3y^2-5x+y+3\\ =-x^2+2y^2-7x+y+2\\ A-B=x^2-2x-y^2-1+2x^2-3y^2+5x-y-3\\ =3x^2-4y^2+3x-y-4\)
\(b,B-D=A\\ \Rightarrow-D=A-B\\ \Rightarrow D=-\left(3x^2-4y^2+3x-y-4\right)\\ \Rightarrow D=4+y+4y^2-3x^2-3x\)
Bài 5 :
a, \(A+B=-x^2+2y^2-7x+y+2\)
\(A-B=3x^2+3x-4y^2-4-y\)
b, \(D=B-A=-2x^2+3y^2-5x+y+3-x^2+2x+y^2+1=-3x^2+4y^2-3x+y+4\)
a) \(A+B=x^2-2x-y^2-1-2x^2+3y^2-5x+y+3=-x^2-7x+2y^2+y+2\\ A-B=x^2-2x-y^2-1-\left(-2x^2+3y^2-5x+y+3\right)\\ =x^2-2x-y^2-1+2x^2-3y^2+5x-y-3\\ =3x^2+3x-4y^2-y-4\)b)\(B-D=A\Leftrightarrow D=B-A=-\left(A-B\right)=-3x^2-3x+4y^2+y+4\)
