a: \(M+\left(12x^2-6xy\right)=3x^2+4xy-2y^2\)
=>\(M=3x^2+4xy-2y^2-12x^2+6xy\)
=>\(M=-9x^2+10xy-2y^2\)
b: \(M-\left(5xy-6y^2\right)=x^2-87xy+6y^2\)
=>\(M=x^2-87xy+6y^2+5xy-6y^2\)
=>\(M=x^2-82xy\)
c: \(\left(-20x^2y+15xy^2-y^3\right)-M=21x^2y-2y^3\)
=>\(M=-20x^2y+15xy^2-y^3-21x^2y+2y^3\)
=>\(M=-41x^2y+15xy^2+y^3\)
d: \(M+\left(12x^4-15x^2y+2xy^2+7\right)=0\)
=>\(M=0-\left(12x^4-15x^2y+2xy^2+7\right)\)
=>\(M=-12x^4+15x^2y-2xy^2-7\)
a) \(M+\left(12x^2-6xy\right)=3x^2+4xy-2y^2\Rightarrow M=3x^2+4xy-2y^2-12x^2+6xy=-9x^2-2y^2+10xy\)
b) \(M-\left(5xy-6y^2\right)=x^2-87xy+6y^2\Rightarrow M=x^2-87xy+6y^2+5xy-6y^2=x^2-82xy\)
c) \(\left(-20x^2y+15xy-y^3\right)-M=21x^2y-2y^3\Rightarrow M=-20x^2y+15xy-y^3-21x^2y+2y^3=-41x^2y+15xy+y^3\)
d) \(M+\left(12x^4-15x^2y+2xy^2+7\right)=0\Rightarrow M=-12x^4+15x^2y-2xy^2-7\)
