（1）因为（1-m）^²=0
|n+2|=0
得：m=1,n=-2
所以：m+n=-1
（2）原式=（1/1×3+1/3×5+1/5×7……+1/17×19）+(1/2×4+1/4×6+1/6×8……+1/18×20)=9/19+9/40=531/760
1/1×3+1/3×5……+1/17×19=1/2(1/3-1/5+1/5-1/7……+1/17-1/19)=1/2×(1-1/19)=9/19
1/2×4+1/4×6+1/6×8……+1/18×20=1/2(1/2-1/4+1/4-1/6……+1/18-1/20)=1/2×(1/2-1/20)=9/40