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先化简,再求值:(1)5xyz%{2x2y%[3xyz%(4xy2%x2...

(1)原式=5xyz-2x2y+3xyz-4xy2+x2y=8xyz-x2y-4xy2.当x=-2,y=-1,z=3时,原式=8×(-2)×(-1)×3-(-2)2×(-1)-4×(-2)×(-1)2=48+4+8=60.(2)原式=-2mn+2m+3n-3mn-2n+2m-m-4n-mn=-6mn+3m-3n.当m-n=2,mn=1,时,原式=-6×1+3×2=0.(3...

①原式=8a-7b-4a+5b=4a-2b;②原式=5xyz-2x2y+3xyz-(4xy2-x2y)=5xyz-2x2y+3xyz-4xy2+x2y=8xyz-x2y-4xy2;③原式=-6m-9n-2n+4m=-2m-11n,当m=5,n=-1时,原式=-2×5-11×(-1)=-10+11=1.

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