Question

Find the missing elements:-
l=486, r=3, Sn=728

Answer 1

a=? and n=?

Answer 2

l=486??what is it

Answer 3

the last term

Answer 4

l=ar^(n-1)

Answer 5

2 equations, 2 unknowns...

Answer 6

486=a . 3^(n-1) ------eqn (i)

Answer 7

S = a (3^n-1)/2=728

Answer 8

3^(n-1)=3^n /3

Answer 9

2*728 = a (3^n)-a ---->from sum formula
3*486 =a*3^n--->from last term
substitute for a*3^n and u get a from 1st equation

Answer 10

got that ^ ?

Answer 11

yeah i did it a=2 and n=6

Answer 12

good :)