Question

What is the coefficient of x^9 in (2+x)12?

Answer 1

And you ment to raise the ^12

Answer 2

I*

Answer 3

General term is
\[T _{r+1}=_{_{r}^{C}}^{12}\left( 2 \right)^{12-r}\left( x \right)^r\]
put r=9
the coefficient of x^9 is
\[C_{9}^{12}\left( 2 \right)^{12-9}=?\]

Answer 4

8?

Answer 5

That was my first answer, I don;t see what I'm doing wrong.

Answer 6

don't

Answer 7

\[C_{9}^{12}2^{12-9}=C _{12-9}^{12}2^{3}=C _{3}^{12}(8)=\frac{ 12*11*10 }{ 3*2*1 }*8=?\]

Answer 8

ohhhhh, so you actually multiple the combination part! Sweet! Thank you!