在某文具商场中，每个画夹定价为20元，每盒水彩定价为5元。为促进销售，商场制定两种优惠方案：一种是买一个画夹赠送一盒水彩；另一种是按总价92％付款。一个美术教师欲购买画夹4个，水彩若干盒（不少于4盒）。
（1）设购买水彩数量为x（盒），付款总金额为y（元），分别建立两种优惠方案中的y与x的函数关系式；
（2）如果购买同样多的水彩，哪种方案更省钱？
解：（1）按优惠方案①可得
y1=20×4+（x-4）×5=5x+60（x≥4），
按优惠方案②可得
y2=（5x+20×4）×92%=4.6x+73.6（x≥4）；
（2）比较
y1-y2=0.4x-13.6（x≥4），
令y1-y2=0，得x=34
∴当购买34盒水彩时，两种优惠方案付款一样多,
当4≤x＜34时，y1＜y2，优惠方案①付款较少；
当x＞34时，y1＞y2，优惠方案②付款较少。
Thanksgiving Day was near. The Grade 7 teacher asked her students to 16 a picture of something for which they were thankful. People celebrated the 17 with turkey and other traditional goods of the season. So, 18 of her students’ pictures were about them. However, Jack made a ___19____ kind of picture. Jack was not the same as other boys. He always looked sad. When asked to draw a picture of something for which he was 20 , he drew a hand. Other students were all very 21 in the picture. Whose hand could it be? One child guessed it was the hand of a farmer, because farmers feed 22 . Another suggested a police officer, because the police 23 and care for people. Still 24 guessed it was the hand of God, for God feeds us. And so the 25 went on until the teacher almost forgot the young artist himself. When the children had gone on to other subjects, she stopped at Jack’s desk and asked him 26 it was. The little boy looked up and said in a 27 voice, “It’s yours, teacher.” She remembered the times she had taken his hand and 28 with him here or there, as she had with the other students. She often said, “ 29 my hand, Jack. We’ll go outside.” Or, “Let me show you how to use your pencil.” Jack was most thankful for his ___30____ hand.
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