• anonymous
From this: $(1+t+t^2)^5=\sum \binom{5}{r_1}\binom{5-r_1}{r_2}t^{r_2}t^{2r_1}$ How do I carry on to find out the values of $r_1$ and $r_2$?
Mathematics

Looking for something else?

Not the answer you are looking for? Search for more explanations.