1.å·²ç¥a+1/a=1+æ ¹å·10,
ç±(a+1/a)^2=a^2+(1/a)^2+2
å(a+1/a)^2=(1+æ ¹å·10)^2=11+2æ ¹å·10
å¾a^2+(1/a)^2+2=11+2æ ¹å·10
a^2+ï¼1/a^2ï¼=9+2æ ¹å·10.
2.å·²ç¥x,y为å®æ°ï¼ä¸y<(æ ¹å·ä¸x-1)+(æ ¹å·ä¸1-x+3)
=(æ ¹å·ä¸x-1)+(æ ¹å·ä¸3-(x-1))<=æ ¹å·ä¸3.
æ ¹å·ä¸y^2-8y+16ï¼
=æ ¹å·ä¸(y-4)^2
=ï¼y-4ï¼çç»å¯¹å¼
æ
ï¼y-3ï¼çç»å¯¹å¼-æ ¹å·ä¸y^2-8y+16ï¼
=ï¼y-3ï¼çç»å¯¹å¼-ï¼y-4ï¼çç»å¯¹å¼
=3-y+y-4=-1.
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