Question

函数f(x)=x分之2加1减2x分之9 (x属于(0,2分之1))的最小值为?急

Answer 1

f(x)=[2x+(1-2x)][2/x+9/(1-2x)]

=13+18x/(1-2x)+2(1-2x)/x

00

13+18x/(1-2x)+2(1-2x)/x>=13+2√[18x/(1-2x)*2(1-2x)/x]=13+12=25

所以最小值=25