[SOLVE]External shared lib and qt ...

Hi all, I'm traying tu use an exteranl shared lib in a mine qt software.. For develop it I'm using QT Creator, I tray to add the line at the pro file:
LIB += -L"/pathtolib" or -l"Name of lib" or only the name of the lib

But nothing to do the result is a linker error:
error: collect2: ld returned 1 exit status

whit some function without reference (off course..)
Some help please! There are 2 days that I work around this problem!

LIBS += -L/path/to/MyLib/ -lMyLib

Mmm, I used also this config but nothing ... The same error..

[EDIT]Mmm I don't see.. the error is not the same the linker output is:
/usr/bin/ld: cannot find -llibkfacebook
but the libkfacebook is installed in the correct path..
[EDIT2]I'm an Idiot.. The right name of the lib is kfacebook also if the file is libkfacebook.. ops.. lol