## anonymous one year ago Showing question 6 of 28 Write the series in summation notation: 100 + 95 + 90 + 85 + 80

• This Question is Open
1. Michele_Laino

here we have a sequence whose first term is a1=80, and 5-th term is 100, furthermore, the constant of your sequence, is: d=100-95=95-90=90-85=85-80=...

2. Michele_Laino

furthermore the general term, namely the n-th term is: $\Large {a_n} = {a_1} + \left( {n - 1} \right)d$

3. Michele_Laino

so the requested sum is: $\Large \sum\limits_{n = 1}^5 {{a_n}} = \sum\limits_{n = 1}^5 {{a_1} + \left( {n - 1} \right)d = ...}$