RT
a,b,c∈R+,1abc+1a+1c=1b,M=4a2+1+4b2+1+7c2+1\small a,b,c\in\R^+,\dfrac{1}{abc}+\dfrac{1}{a}+\dfrac{1}{c}=\dfrac{1}{b},M=\dfrac{4}{a^2+1}+\dfrac{4}{b^2+1}+\dfrac{7}{c^2+1}a,b,c∈R+,abc1+a1+c1=b1,M=a2+14+b2+14+c2+17
求 Mmax.M_{\max}.Mmax.
首先应该是 a=tanα,b=−tan(α−β),c=tanβa=\tan \alpha,b=-\tan(\alpha-\beta),c=\tan \betaa=tanα,b=−tan(α−β),c=tanβ ？
