Question

A gp has common ratio =3 and last term = 486 if the sum of its term is 728 find its first term

Answer 1

Hey mate, here is your answer.
By using the formula, S=lr-a/r-1

S=728
l=486
r=3
a=?

728=486×3-a/3-1
728×2=486×3-a

1456 = 1458-a

a = 1458-1456

a=2
is your answer.

Hope it will help you.

Answer 2

now putting the value of n in (1) or (2) we get a= 2.
$thus \: the \: g \: p \: has \: 6 \: terms \: and \: its \: first \: term \: is \: 2$