| 先化简，再求值： （1）（3x2y-xy2）-3（-2xy2+x2y），其中x=
（2）3x3-[x3+（6x2-7x）]-2（x3-3x2-4x），其中x=-1． |
（1）原式=3x2y-xy2+6xy2-3x2y=5xy2，
∵x=
，y=-1 2
，1 3
∴原式=
；5 18
（2）原式=3x3-x3-6x2+7x-2x3+6x2+8x=15x，
∵x=-1，
∴原式=-15．
| 完形填空。 | ||||
| When July comes, children know they'll have their examinations and the school year will 1 soon. Boys and girls will have nearly a two-month holiday, and they'll leave school 2 train or by car to 3 their parents. The summer holidays are the 4 time of the year for most children. The weather is usually good, so children can spend most of their time 5 outside. If one lives in the countryside, he can go and play in the woods or in the fields. If he 6 in a big town, he can usually go to the park to play. The best place for children to spend their summer holidays is the 7 . Some children are lucky enough to live near the sea. 8 for those who do not live there, if they have the luck to stay in one of the big seaside towns for a week or two, they'll 9 it all the following school year. Now, 10 makes children like the seaside so much? I think they are the sand, the sea and the sun. The feelings of the sand under their feet, salt water on their skin, and the warm sun on | ||||
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