# SERIES....AND SEQUENCE....

Let a,b,c be three distinct positive numbers which are in G.P.

If logca , logbc , logab are in A.P., then the common difference of the A.P. is....

1
ANKIT MAHATO ·

Tragedy !!

1
Gaurav Lodhi ·

Wrong that is cubic equation

1
prateek punj ·

yup...got u ....thnx.....more coming now....

1
vector ·

edited i hope its kk now[1]

1
prateek punj ·

it's just all correct but just edit logar=t.....

1
vector ·

actually i think u get confused as i took variable same as a waitt i m editting

1
prateek punj ·

hey richa i think there is some problem in ur solution i think u have taken...

logbr=t....but u have written logar=t.....

plssss just check it out....

1
vector ·

prateek logab-logbc is common diff

1
prateek punj ·

yaaar jaldi reply karo aur bhi series ke question hain...

1
ANKIT MAHATO ·

hats off to richa !!

1
prateek punj ·

yaar how t2/1-t gives the value of common difference.....

1
ANKIT MAHATO ·

abt this sum ..

1
vector ·

bt it s not at all a short approach
let a,b,c be A/r,A,Ar
let logAr=t
i took all log to base b(or u cud say toA)
so wat s given is
2(1+t)=1/(1-t)+(1-t)/1+t
solving it we get
2t2+3t-3=0
2t2=3(1-t)
t2/1-t=3/2
as we ve to find the value of common difference
its = t2/1-t
so here is d ans ne short approach is invited [1]

1
prateek punj ·

1
prateek punj ·

anyone....

1
prateek punj ·

yaar koi isse bhi solve karo....[79]

1
prateek punj ·

yaar abhi tak kissi ne solution nahin diya.....what has happened to u tiitians.......

1
prateek punj ·

anyone else plzzz help it out yaar....

1
prateek punj ·

yeah it's long....can anyone give a shorter method.....becoz it's a multiple choice ques.....so required shorter method.....

1
sriraghav ·

that was a mistake which i posted earlier

log c / log b - log a / log c= diff..

log c= log a + 2 log r

log b = log a + log r

sub in 1 and reduce it... u hav to get it...but it is long i think so..

1
prateek punj ·

okkaaaa

1
sriraghav ·

wait a min prateek

1
prateek punj ·

koi toh batao.....[79]

1
prateek punj ·

anyone plzzz solution batao....

1
prateek punj ·

arey yaar ankit....main yeh sab kar chuka hoon....par answer nahin aa raha....it's a finite value....

1
ANKIT MAHATO ·

logca + logab =2 logbc

log a / log c + log b / log a = 2log c / log b

a
b = ar
c = ar2

now proceed

.....

1
sriraghav ·

log (ab) / log c