答:
当x>0时:
(x²+5x+6)/(6x)
=(1/6)(x+6/x+5)
>=(1/6)(2+5)
=7/6
当x
答:设t=6x+1,x=(t-1)/6原式=(x²+5x+6)/(6x+1)=(x+2)(x+3)/(6x+1)=[(t-1)/6+2]*[(t-1)/6+3]/t=(t+11)(t+17)/(36t)=(t²+28t+187)/(36t)=(1/36)(t+187/t+28)>=(1/36)(2√187+28)t>0时=√187/18+7/9原式=(1/36)(t+187/t+28)
实在不好意思是x2+5x+6/6X+6当X>0是,求最小值
原式=(x²+5x+6)/(6x+6)=(1/6)*[(x+1)²+3(x+1)+2]/(x+1)=(1/6)*[(x+1)+2/(x+1)+3]>=(1/6)(2√2+3)=√2/3+1/2所以:最小值为√2/3+1/2