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问题: 高考在即很急!!

解答:

y=x²/2--->y'=x
设P(2p,2p²),Q(2q,2q²)--->M(p+q,p²+q²)
--->切线斜率k=2p
--->k(PQ)=(2p²-2q²)/(2p-2q)=p+q=-1/(2p)
--->q=-p-1/(2p)
--->yM=p²+q²=p²+[p²+1+1/(4p²)]=2p²+1/(4p²)+1≥√2+1......B