(1)m-n=-2 4-2m+2n=4-(2m-2n)
-m+n=n-m =4-2(m-n)
=-(m-n) =4-2(-2)
=2 =4-(-4)
=0
(2)原式=2a+3b-2ab-a-4b-ab-3ab-2b+2a
=3a-3b-5ab
=3(a-b)-5ab
其中a-b=5,ab=1,原式=3*5-5*1=15-5=10
(1)m-n=-2 4-2m+2n=4-(2m-2n)
-m+n=n-m =4-2(m-n)
=-(m-n) =4-2(-2)
=2 =4-(-4)
=0
(2)原式=2a+3b-2ab-a-4b-ab-3ab-2b+2a
=3a-3b-5ab
=3(a-b)-5ab
其中a-b=5,ab=1,原式=3*5-5*1=15-5=10