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【单选题】
函数f(x,y)=(6x−x2)(4y−y2)f(x,y)=(6x−x2)(4y−y2)的极值为A.
f ( 3 , 2 ) = 36 " role="presentation" style="display: inline-block; line-height: 0; font-size: 19.52px; overflow-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; margin: 0px; padding: 1px 0px; color: rgb(0, 0, 0); font-family: "Microsoft YaHei"; position: relative;" > f ( 3 , 2 ) = 36 f(3,2)=36
B.
f ( 3 , 0 ) = 0 " role="presentation" style="display: inline-block; line-height: 0; font-size: 19.52px; overflow-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; margin: 0px; padding: 1px 0px; color: rgb(0, 0, 0); font-family: "Microsoft YaHei"; position: relative;" > f ( 3 , 0 ) = 0 f(3,0)=0
C.
f ( 0 , 2 ) = 0 " role="presentation" style="display: inline-block; line-height: 0; font-size: 19.52px; overflow-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; margin: 0px; padding: 1px 0px; color: rgb(0, 0, 0); font-family: "Microsoft YaHei"; position: relative;" > f ( 0 , 2 ) = 0 f(0,2)=0
D.
f ( 3 , 2 ) = 6 " role="presentation" style="display: inline-block; line-height: 0; font-size: 19.52px; overflow-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; margin: 0px; padding: 1px 0px; color: rgb(0, 0, 0); font-family: "Microsoft YaHei"; position: relative;" > f ( 3 , 2 ) = 6 f(3,2)=6
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举一反三
【单选题】What does the author mean by saying 'we are encouraged to hop when we have two perfectly good legs' (Para. 4) ?
A.
We needn't hop because we are healthy.
B.
Only those who have something wrong in their legs can be encouraged to hop.
C.
It's foolish of us to hop when we have two perfectly good legs.
D.
We should use both sides of the brain.