Question

write the following sequence in an form and find the value of the 15th term 4,9,14,19. What is the sum of the first 15 terms of the above sequence?

Answer 1

Opening question: What is the pattern in this sequence? In other words, how do we get the next term, and the next, and the next...

Answer 2

add 5 would the equation be an=-1 + 5n?

Answer 3

it is an arithmatic progresion.series....
a = 4, d= 5, n=15
sum of 15 terms S15= n/2[ 2a +(n-1)d]
= 15/2[ 8+14*5]
= 15/2[78]
= 15*39
= 585

Answer 4

the formula for sum is s of n= n(a sub 1 + a sub n) divided by 2

Answer 5

15 th term = a+(n-1)d
= 4 + 14*4
=60

Answer 6

i got 59..

Answer 7

sorry, it is 4 + 14*5 = 74

Answer 8

ok and what is the equation of the sequence in a sub n form

Answer 9

do you have aim?

Answer 10

already written.........
a = first term
d= common difference
n= number of terms

Answer 11

no it has to be like an=-1+5n is that right?

Answer 12

for nth term a+(n-1)d

for sum of first n terms n/2[2a +(n-1)d]

Answer 13

yeah iknow but you plug in a as 4 and d as 5 and simplify what you can i thought?

Answer 14

if you have problem to understand it , you r welcome to talk to me using skype, i m unable to explain it..........
skype id : sudhanshu_kmr

Answer 15

do you have instant messenger?

Answer 16

no......

Answer 17

ok another question for you:\[\sum_{n=1}^{3}i^n-1\]

Answer 18

its i to the n-1 power

Answer 19

i +i^2 +i^3 -1 = i -1 - i -1= -2

as i^2 = -1, i^3 = -i

Answer 20

i ended up with an answer of i?