计算:(-100)×(-1)×(-3)×(-0.5);
计算:0.1×(-0.001)×(-1);
计算:-6×(-5)×(-7);
计算:-2×3×(-4);
1×a=_____, (-1)×a=______
1×(-5)=______,(-1)×(-5)=_______,+(-5)=______,-(-5)=______;