What are the first five partial sums of the arithmetic sequence an = 0.05 (n - 1) - 0.6?

The sum of the arithmetic sequence given by

an = 0.05 (n - 1) - 0.6

will be given by:

a1=0.05 (1-1) - 0.6=-0.6

a2=0.05 (2-1) - 0.6=-0.55

a3=0.05 (3-1) - 0.6=-0.5

a4=0.05 (4-1) - 0.6=-0.45

a5=0.05 (5-1) - 0.6=-0.4

thus the summation will be:

-0.6 + (-0.55) + (-0.5) + (-0.45) + (-0.4)

=-2.5

hence

S5=-2.5