i have a hw problem that i have problem solving.
w + x+ y + z = 12
how many nonnegative interger solutions are there?
well, using the "r-combinations w/ repitition allowed" rule u get
3 seperators so the answer would be C(12+3,12) -> C(15,12)
ok, here''s what i have the problem in:
w needs to be 0 <= w <= 4, meaning it can only be 0,1,2,3,or 4
having a hard time with this... please help
and if any1 cares, this is how i did it. total poss: C(15,12) = 455 subtract the ones outside each range for each variable 455-120-84-20-10 then since the subtracted #''s overlap by 4, u add 4 resulting in 225.