How do i convince my mom to let me get a facebook?

my mom says she trust me...but obviously thts not true if she doesnt let me get a facebook. i tld her ALL my friends hav one (except 2) and thts a lot of ppl. it anoys me caz evry1s lke OMG get a facebook, and i cnt..facebook is how u become friends with ppl in older grades and im lke one of the only ones thts not rele good friends (enough 2 hang out with) older kids..help