取x1>x2>10 (x1-x2)>0
f(x1)-f(x2)=
lg[(ax1-1)/(x1-1)]-lg[(ax2-1)/((x2-1)]
=lg[(ax1-1)(x2-1)]/[(x1-1)(ax2-1)]
>0
[(ax1-1)(x2-1)]/[(x1-1)(ax2-1)]>1
[ax1x2-ax1-x2+1]/[ax1x2-ax2-x1+1]>1
当a>1/10时
[(ax1-1)(x2-1)]>[(x1-1)(ax2-1)]
-ax1-x2>-ax2-x1
ax1+x2
取x1>x2>10 (x1-x2)>0
f(x1)-f(x2)=
lg[(ax1-1)/(x1-1)]-lg[(ax2-1)/((x2-1)]
=lg[(ax1-1)(x2-1)]/[(x1-1)(ax2-1)]
>0
[(ax1-1)(x2-1)]/[(x1-1)(ax2-1)]>1
[ax1x2-ax1-x2+1]/[ax1x2-ax2-x1+1]>1
当a>1/10时
[(ax1-1)(x2-1)]>[(x1-1)(ax2-1)]
-ax1-x2>-ax2-x1
ax1+x2