已知多项式5x^2-2mxy-13y^2-x+y-1与4x^2-2xy-10y^2+x-y+1的和不含xy项,求2008

(5x^2-2mxy-13y^2-x+y-1)+(4x^2-2xy-10y^2+x-y+1)
=5x^2-2mxy-13y^2-x+y-1+4x^2-2xy-10y^2+x-y+1
=9x^2-(2m+2)xy-23y^2
不含xy项
所以系数为0
-(2m+2)=0
2m+2=0
m=-1