解方程3log(x)4+2log(4x)4+3log(16x)4=0

4个回答

  • 解方程3log‹x›4+2log‹4x›4+3log‹16x›4=0

    将真数和对数互换得:3/log₄x+2/log₄4x+3/log₄16x=0

    即有3/log₄x+2/(1+log₄x)+3/(2+log₄x)=0

    令log₄x=u,则上式变为3/u+2/(1+u)+3/(2+u)=0

    去分母得3(1+u)(2+u)+2u(2+u)+3u(1+u)=0

    展开化简得4u²+8u+3=(2u+1)(2u+3)=0,故u₁=-1/2;u₂=-3/2.

    由log₄x=-1/2,得x₁=4^(-1/2)=1/√4=1/2;

    由log₄x=-3/2,得x₂=4^(-3/2)=1/√64=1/8.