Question

Find the second term of the arithmetic series described by a1=0.25, an=4, and sn=8.5 answer: a2=

Answer 1

Explanation:

an=4=a1+(n-1)*d=0.25+(n-1)*d

so (n-1)*d=4-0.25=3.75

Sn=a1*n+(n-1)*d

a1*n+3.75=8.5

0.25*n+3.75=8.5

-3.75 -3.75

0.25*n=8.5-3.75=4.75

n=4.75:0.25

n=19

so a19=a1+(19-1)*d=4

0.25+18*d=4

-0.25 -0.25

18*d=3.75

d=3.75/18

d=0.208

so a2=a1+0.208=0.25+0.208=0.458

a2=0.458