a) \(A+B=15x^2y-7xy^2-6y^3+2x^3-12x^2y+7xy^2=2x^3+3x^2y-6y^3\)
\(A-B=15x^2y-7xy^2-6y^3-2x^3+12x^2y-7xy^2=-2x^3-6y^3+27x^2y-14xy^2\)
A+B = \(13x^2y-6y^3+2x^3\)
A-B = \(27x^2y-6y^3-2x^3\)
\(A+B=13x^2y-6y^3+2x^3\) tại x=1 ,y=3
\(A+B=13.1^2\)\(.3\) - \(6.3^3\)+\(2.1^3\)
A+B = 13.1.3 - 6.27 + 2.1
A+B = 39 - 162 + 2
A+B= -128
A-B = \(27.1^2.3-6.3^3-2.1^3\)
A-B = 27.1.3 - 6.27-2.1
A-B = 81 - 162 - 2
A-B = -83
a) A+B = 13x2y−6y3+2x313x2y−6y3+2x3
A-B = 27x2y−6y3−2x327x2y−6y3−2x3
b) A+B=13x2y−6y3+2x3A+B=13x2y−6y3+2x3 tại x=1 ,y=3
A+B=13.12A+B=13.12.3.3 - 6.336.33+2.132.13
A+B = 13.1.3 - 6.27 + 2.1
A+B = 39 - 162 + 2
A+B= -128
A-B = 27.12.3−6.33−2.1327.12.3−6.33−2.13
A-B = 27.1.3 - 6.27-2.1
A-B = 81 - 162 - 2
A-B = -83