log2f(a)=2,
f(a)=2^2=4=a^2-a+k
f(log2a)=k
(log2a)^2-log2a+k=k
(log2a)^2=log2a
所以log2a=0或log2a=1
即a=1或a=2
因为a大于0且a不=1
所以a=2
代入4=a^2-a+k
k=2
所以
f(x)=x2-x+2
f(log2x)=(log2x)^2-log2x+2>f(1)=2
(log2x)^2-log2x>0
log2x>1或log2x2或0