BV15i4y1N7Nd

A.

729＜1728

即3^6＜12^3

即log(3)(3^6)＜log(3)(12^3)

即6·log(3)(3)＜3·log(3)(12)

即6·1＜3·log(3)(12)

即6z＜3x

ln3/3＞ln4/4

即4ln3＞3ln4

即ln3^4＞ln4^3

即3^4＞4^3

即3^(1/3)＞4^(1/4)

即log(12)(3^(1/3))＞log(12)(4^(1/4))

即1/3log(12)(3)＞1/4log(12)(4)

即1/(3·log(3)(12))＞1/(4·log(4)(12))

即3·log(3)(12)＜4·log(4)(12)

即3x＜4y

綜述

6z＜3x＜4y

C.

log(3)(4)，log(4)(3)＞0

且log(3)(4)≠log(4)(3)

即2+log(3)(4)+log(4)(3)＞4

即1+log(3)(4)+1+log(4)(3)＞4

即log(3)(12)+log(4)(12)＞4·1

即x+y＞4z

ps.

新朋友詳見

CV10088620