In this formula, what is r? I think it is the column of the pascal´s triangle I want, but I am not sure if the first column is column 1 or column 0

Question

osanseviero · Answer

$$\left(\begin{matrix}n \ r\end{matrix}\right)a ^{n-r}b ^{r}$$

osanseviero · Answer

n is the exponent...but r...i dont know

amistre64 · Answer

r is the position of the term in the row

osanseviero · Answer

but is the first position (always 1) counted? or it counts as term 1?

osanseviero · Answer

as term 0*

osanseviero · Answer

For example, if I want the middle term of (a+b)^12, I know I want the sixth term. r should be 5 or 6?

amistre64 · Answer

(a+b)^n, pick the rth term is what im thinking

amistre64 · Answer

(a+b)^3 = a^3 + 3a^2b + 3ab^2 + b^3

hmmm

amistre64 · Answer

3c0  3c1 3c2 3c3  are the coeefs that correspond to ncr

osanseviero · Answer

ok...then a^3 is term 0

osanseviero · Answer

so, r could be the term I want -1...thanks

amistre64 · Answer

sounds good :)