数学`.
证明y=x+k/x...(k大于0)在(-∞,-根号k]为增函数.
y=f(x)=x+k/x 设x1k>0,x1*x2-k>0 ∴f(x1)-f(x2) =(x1+k/x1)-(x2+k/x2) =(x1-x2)+(k/x1-k/x2) =(x1-x2)+k(x2-x1)/(x1*x2) =(x1-x2)[1-k/(x1*x2)] =(x1-x2)(x1*x2-k)/(x1*x2)0)在(0,√k)为增函数
问:高二数学证明不等1+1/根号2 +1/根号3 + 一直加 + .....+1/根号n <2根号n (n属于N+)
答:证明:1+1/√2+1/√3+……+1/√n =1+2/2√2+2/2√3+……+2/2√n <1+2/(√2+1)+2/(√3+√2)+……+2/(√n+√(...详情>>
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