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求f(x)=x2+2x+1/x-1(x>1)的值域
人气:320 ℃ 时间:2020-08-15 09:01:40
解答
f(x)=(x²+2x+1)/(x-1)=(x²-2x+1+4x-4+4)/(x-1)=[(x-1)²+4(x-1)+4]/(x-1)=(x-1)+4+4/(x-1)因为x>1,所以x-1>0故(x-1)+4/(x-1)≥2√[(x-1)×4/(x-1)]=4,此时x=3故f(x)≥4+4=8所以值域为[8,+∞)...
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