The given series is
\[ \sum_{k=1}^{\infty} 5\left(\frac{1}{4}\right)^{k-1}. \]
The first term \( a \) is the term when \( k = 1 \), which is
\[ a = 5\left(\frac{1}{4}\right)^{1-1} = 5\left(\frac{1}{4}\right)^{0} = 5. \]
The common ratio \( r \) is the
Show more…