Question

Which expression defines the given series for seven terms?
9 + 17 + 25 +..

Answer 1

∑(1+8n)

Explanation:

Given:

series : 9+17+25+...

As first term= 9

for n=1, expression should comes out to be 9

for 2+7n:

2+7(1)=9

for (n+8)

1+8=9

for (1+8n)

1+8(1)=9

all is true

now for n=2, the expression's outcome be 17

for 2+7n:

2+7(2)=16

comes wrong

for (n+8)

2+8=10

comes wrong

for (1+8n)

1+8(2)=17

come right

Also for n=3, (1+8(3))=25

Hence correct expression is ∑(1+8n) !