Find the sum of the first 25 terms of the arithmetic series: -5, -4, -3, -2, -1, …

**Solution:-**

Find a_{n} by using the explicit formula for arithmetic sequences:

a_{n} = a_{1} + (n-1)d.

a_{1 }= -5

a_{25} = 19

The use the formula for the sum of an arithmetic series:

S_{n} = (a_{1} + a_{n})

175