= 
= 
= 
= 
= 
= 
= 
……….(i)
Now 
for all real 
as 
. Also 
> 0
(i) 
is increasing if 
, i.e., from eq. (i), 
lies in I and IV quadrants, i.e., is increasing for 
and 
and (ii) is decreasing if 
, i.e., from eq. (i), 
lies in II and III quadrants, i.e., is decreasing for 