Re: [考古] 數題考古題
※ 引述《darkstar0412 (目標當個米蟲廢物公務員)》
: 4.y=2x-10 ,find the values for xand y such that thier product is a minimun.
y=2x-10
=>(y+10)/2=x
=>(y^2+10y)/2 =xy
=>xy=(y^2+10y)/2 ={(y+5)^2-25}/2 >= -25/2
等號在y=-5時成立 代入 y=2x-10 得x=5/2
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