I need to find the number of solutions of the equation $a + b + c + d = 19$ where $a,b,c,d \in ${$0,1,2,...,9$}.
I came up with $(1+z+z^2+...+z^9)^4$
But now I am kind of stuck and do not know how to compute $[z^{19}] (1+z+z^2+...+z^9)^4$
Asked
Active
Viewed 47 times
0
-
Do you know how to first compute $(1+z+z^2+...+z^9)^2$? – Somos Dec 04 '22 at 20:39
-
So I am getting the number of solutions are 660, would that be correct? – jjbinks Dec 05 '22 at 08:33
-
That is correct. – Sil Dec 08 '22 at 03:55