已知多项式A和B,A=(5m+1)x2+(3n-2)xy-3x+y,B=6x2-5mxy-2x-1,当A和B的差不含二次项时,求(-1)m-n[-m+n-(-n)3m]的值.

问题描述:

已知多项式A和B,A=(5m+1)x2+(3n-2)xy-3x+y,B=6x2-5mxy-2x-1,当A和B的差不含二次项时,求(-1)m-n[-m+n-(-n)3m]的值.

A-B=(5m+1)x2+(3n-2)xy-3x+y-(6x2-5mxy-2x-1)=(5m+1)x2+(3n-2)xy-3x+y-6x2+5mxy+2x+1=(5m-5)x2+(5m+3n-2)xy-x+y+1,已知A和B的差不含二次项,∴5m-5=0,5m+3n-2=0,得:m=1,n=-1,∴(-1)m-n[-m+n-...