answer

answer Q no 18.

2 Answers

its proof
it wil not n aksed in JEE

1357

Manish Shankar ·2009-04-11 03:01:43

a,b,c,d are in GP so let b=ar, c=ar², d=ar³

from the equations

a+b=3=a+ar=a(1+r) (sum of roots) (1)
and ab=p

similarly c+d=12=ar²+ar³=ar²(1+r) (2)
and cd=q
from (1) and (2) we get r²=4

(c+d
(q+p)/(q-p)=(cd+ab)/(cd-ab)=(r⁴+1)/(r⁴-1)=17/15

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