state all possible rational zeros for the function

here is one of the problems i'm having trouble with:

f(x)= x^3+2x-3x+5

i know: p= +1, -1, +5, -5

q= same

but none of them seem to equal to zero when i put them in (Headbang)<---me

one that i have NO IDEA how to do is:

find all rational zeros for each function

f(x)= (x-3)(x+5)(2x+5)

Thanks for any help in advance -Liza