Question

Write each of the sums in Exercises 21–28 in sigma notation. Identify $m,n,a_k$in each problem.

$9+12+15+18+21+24+27$

Short answer

The sigma notation is$\sum _{k=3}^{9}3k\mathrm{and}m=3,n=9,a_k=3k$

Step-by-step solution

Step 1. Given Information   

The given sum is $9+12+15+18+21+24+27$

Step 2. Explanation    

The sum in sigma notation is written as,

$$\begin{gathered} 9+12+15+18+21+24+27=\left(3\times 3\right)+\left(3\times 4\right)+\left(3\times 5\right)+\left(3\times 6\right)+\left(3\times 7\right)+\left(3\times 8\right)+\left(3\times 9\right) \\ =\sum _{k=3}^{9}3k \\ where, \\ m=3,n=9,a_k=3k \end{gathered}$$