A.P/G.P/H.P

if a,b,c are in A.P p,q,r are in H.P and ap,bq,cr are in G.P THEN PR+RP IS
(1) AC-CA
(2) AC+CA
(3) BQ+QB
(4) BQ-QB

5 Answers

62
Lokesh Verma ·

preeti.. is it PR + RP??

Bcos then you could as well have aksed 2PR!!??

1
preeti kochar ·

sorry
it is p/r+r/p

1
skygirl ·

if its objective , i can help :)

take a=b=c=1, p=q=r=1.
then ap=bq=cr=1

then for p/r+r/p = 2 , we can eliminate options 1 and 4.
since they will give 0.

now take some suitable value : a=1,b=2,c=3
p=1,q=1/2 , r=1/3

then ap=1, bq=1, cr=1

for these values we have, p/r+r/p=3+1/3

so clearly the same value is given by c/a+a/c.

hence opton (a) is correct .. :)

is 'a' correct b/w (90% sure :P) ;)

1
Prashant Shekhar ·

we have

b2q2=acpr ...(1)
2b=a+c ........(2)
2/q=(p+r)/pr ......(3)

substitute b and q from (2) and (3) and put it in (1)

(a+c)2/4 * 4p2r2/(p+r)2=acpr
or
(p+r)2/pr=(a+c)2/ac

or p/r+r/p=a/c+c/a

1
skygirl ·

yiipppeeeeee!! i was correct :) though it was not 'maths'.. but still .. ;)

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