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Mathematics
Mathematics
Problem
14. Prove that
∑
r
=
0
n
3
r
n
C
r
=
4
n
\sum_{r=0}^{n} 3^{r}{ }^{n} \mathrm{C}_{r}=4^{n}
∑
r
=
0
n
3
r
n
C
r
=
4
n
.
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