Here is an example to use the CAS for the BAC 2013 (french exam)
http://www.lexpress.fr/education/bac-2013-le-sujet-de-maths-et-son-corrige_1259225.html
EXERCICE 2
Keystroke :
(a+b*LN(x))/x STO> f(x)
f'
Simplif
solve([f(1)=2;f'(1)=0],[a,b])
2 STO> a
2 STO> b
f(x)
simplif
lim x->0 f(x)
lim x->+oo f(x)
Screen display :