Question

高一对数函数的几道数学题1.已知f(x)=丨In x丨,则下列不等式成立的是：A.f(1/3)＞f(2); B.f(1/

Answer 1

f(1/3) = |ln1/3| = -ln1/3 = ln3,f(1/2) = |ln1/2| = -ln1/2 = ln2

因lnx在定义域增函数,故A

f为分段函数,所以要求ff(1/2),首先1/2>0,所以f(1/2)=log2 1/2 = -1,而-1<0,所以f(-1)=3^(-1)=1/3.即f(f(1/2))=f(-1)=1/3

(x-1)^2log4(a)+2x = 0,即log4(a)x^2+[2-2log4(a)]x+log4(a)=0

无实数根,则△<0,即 [2-2log4(a)]^2-4log4(a)^2<0

4-8log4(a)<0

log4(a)>1/2=log4(2)

a>2