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求答案!急急急大家帮帮忙!谢谢
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解:(1) 3(xy-2z)+(-xy+3z)
=3xy-6z-xy+3z
=2xy-3z
(2) -4(pq+pr)+(4pq+pr)
=-4pq-4pr+4pq+pr
=-3pr
(3) (2x-3y)-(5x-y)
=2x-3y-5x+y
=-3x-2y
=3xy-6z-xy+3z
=2xy-3z
(2) -4(pq+pr)+(4pq+pr)
=-4pq-4pr+4pq+pr
=-3pr
(3) (2x-3y)-(5x-y)
=2x-3y-5x+y
=-3x-2y
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