If Sn denotes the sum of first n terms of an A.P. <an> such that SmSn=m2n2, then aman=
2m−12n−1
SnSn=m2n2
⇒m2{2a+(m−1)d}m2{2a+(n−1)d}=m2n2
⇒{2a+(m−1)d}{2a+(n−1)d}=mn
⇒2an+ndm−nd=2am+nmd−md
⇒2an−2am−nd+md=0
⇒2a(n−m)−d(n−m)=0
⇒2a(n−m)−d(n−m)
⇒d=2a……(1)
Ratio of aman=a+(m−1)da+(n−1)d
⇒aman=a+(m−1)2aa+(n−1)2a From (1)
=a+2am−2aa+2an−2a
=2am−a2am−a=(2m−1)(2n−1)