Question

Which spreadsheet would be used to compute the first five partial sums o the arthmetic series? an=-5(n-1)+8

Answer 1

The nth term of the arithmetic series is given by

$a_n=-5(n-1)+8$

Now find the first five terms $a_1, a_2, a_3, a_4, a_5:$

$a_1=-5(1-1)+8=8$

$a_2=-5(2-1)+8=3$

$a_3=-5(3-1)+8=-2$

$a_4=-5(4-1)+8=-7$

$a_5=-5(5-1)+8=-12$

Thus the first five terms of the series is $8,3,-2,-7,-12.$

Now find the partial sum of the series:

$S_1=a_1=8$

$S_2=a_1+a_2=8+3=11$

$S_3=a_1+a_2+a_3=8+3-2=9$

$S_4=a_1+a_2+a_3+a_4=8+3-2-7=2$

$S_5=a_1+a_2+a_3+a_4+a_5=8+3-2-7-12=-10$