Question

1:已知多项式x^2+2axy-xy^2与多项式3xy-axy^2-y^3的和不含xy项,求其和

Answer 1

1:已知多项式x^2+2axy-xy^2与多项式3xy-axy^2-y^3的和不含xy项

所以2a=-3 a=-3/2

x^2+2axy-xy^2+3xy-axy^2-y^3

=x^2-xy^2+1/2xy^2-y^3

2:(2mx^2-x^2+3x+1)-(5x^2-4y^2+3x)不含x^2项

所以2mx^2-x^2+3x+1-5x^2+4y^2-3x

(2m-1-5)x^2=0

m=3

2m^3-[3m^2+(4m-5)+5]

=2*3^3-[3*3^2+(4*3-5)+5]

=15