因为n-m=-3
所以
m-n
= -(n-m)
= -(-3)
=3
-1+m-n
=-1-(n-m)
=-1-(-3)
=-1+3
=3-1
=2
4-2m+2n
=4+2n-2m
=4+2(n-m)
=4+2×(-3)
=4+(-6)
=-(6-4)
= -2