hey guys,

my lecturer skipped the proof to show that is a generating function of the polynomials,

he told us that we should do it as an exercise by first finding the binomial series of

then insert s = -u^{2}+ 2xu

he then said to expand out s^{n}and group together all the u^{n}terms,

this is what i've been doing for a while and i haven't been able to see the end,

is my approach incorrect?