当xy为何值时,式子a=-x方一y方十2x十6y十6具有最小值
题目
当xy为何值时,式子a=-x方一y方十2x十6y十6具有最小值
答案
a=-x方一y方十2x十6y十6
=-x²+2x-y²+6y+6
=-x²+2x-1-y²+6y-9+6+10
=-(x²-2x+1)-(y²-6y+9)+16
=-(x-1)²-(y-3)²+16
当x=1,y=3时,有最小值为16
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