单选题If 7/x+2/y=7 and xy=4, then 7y+2x= ______.A28B14C7/4D4/77E2/7
单选题
If 7/x+2/y=7 and xy=4, then 7y+2x= ______.
A
28
B
14
C
7/4
D
4/77
E
2/7
参考解析
解析:
将7/x+2/y=7化简得7y+2x=7xy,所以原式=28,故本题选A项。
将7/x+2/y=7化简得7y+2x=7xy,所以原式=28,故本题选A项。
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