先化简,再求值 ⒈2(Xy+Xy)-3(Xy-xy)-4Xy,其中X=1,y=-1

1.2(Xy+Xy)-3(Xy-xy)-4Xy
=2*2xy-0-4xy
=4xy-4xy
=0
2.1/2ab-5aC-(3ac b)+(3aC-4a C)
=1/2ab-5ac-3acb-ac
=1/2ab-6ac-3acb
=1/2ab-3ac(2+b)
当a=-1,b=2,c=-2时
1/2ab-3ac(2+b)
=1/{2(-1)*2}-3(-1)（-2）（2+2）
=1/(-4)-24
=-0.25-24
=-24.25