Sequence And Series

Question 1

Nth term of an AP

Answer 1

a(n)=a+(n-1)d

Question 2

Sum of n terms of an AP?

Answer 2

S(n)=n/2 [2a+(n-1)d]

Question 3

Arithmetic mean of n numbers A=?

Answer 3

A= a1+a2+……+aN/N

Question 4

Inserting n AM’s between 2 numbers a,A1,A2,….An,b, common difference d=?

Answer 4

d= b-a/n+1

Question 5

In arithmetic progression , aN + a’N=?

Answer 5

aN+a’N=a+l

; aN and a’N are nth terms of an AP from first and last term respectively

Question 6

a,b,c are 3 consecutive terms of an AP. 2b=?

Answer 6

2b= a+ c

Question 7

Tn= nth term of an AP from first term , then Tn=?

Answer 7

T(n)=S(n)-S(n-1)

Question 8

Nth term of a GP

Answer 8

a(n)=ar^n-1

Question 9

Nth term of a GP from the end

Answer 9

a’n=l/r^n-1

Question 10

Sum of n terms of a GP

Answer 10

S(n)=a(r^n-1)/r-1

Question 11

Sum of n terms of a GP when last term is known

Answer 11

S(n)=a-lr/1-r

Question 12

b,c, and d are three consecutive terms of a GP. c^=?

Answer 12

c^=bd