Given,
C1+3.2C2+5.3C3+ ...... upto 10 terms
=2β−1α.211 (C0+2C1+3C2 + ..... upto 10 terms)
Now,
L.H.S. :-
C1+3.2C2+5.3C3+ ...... upto 10 terms
=1.1C1+3.2C2+5.3C3+ ..... upto 10 terms
=r=1∑10r.(2r−1)10Cr
=r=1∑10(2r2−r).10Cr
=2.r=1∑10r2.10Cr−r=1∑10r.nCr
[We know, r=1∑nr.nCr=n.2n−1
and r=1∑nr2.nCr=r=1∑n(r.nCr).r
=r=1∑n(r.rn.n−1Cr−1).r
=r=1∑n(n.n−1Cr−1).r
=nr=1∑n(r−1+1)n−1Cr−1
=n.r=1∑n(r−1).n−1Cr−1+n.r=1∑nn−1Cr−1
=n.(n−1).2n−2+n.2n−1]
=2(n(n−1)2n−2+n.2n−1)−n.2n−1
Put n=10
=2(10.9.28+10.29)−10.29
=45.210+10.210−5.210
=210(45+10−5)
=210.(50)
=25.211
R.H.S. :-
2β−1α.211 (C0+2C1+3C2+ ..... upto 10 terms)
2β−1α.211 (1C0+2C1+3C2+ ..... upto 10 terms)
2β−1α.211(r=0∑nr+1nCr)
=2β−1α.211(r=0∑nn+1n+1Cr+1)
=2β−1α.211(n+1n+1C1+n+1C2+....+n+1Cn+1)
=2β−1α.211(n+1n+1C0+n+1C2+....+n+1Cn+1−n+1C0)
=2β−1α.211(n+12n+1−1)
Putting value of n=10, we get
=2β−1α.211(11211−1)
Using L.H.S. = R.H.S.
⇒25.211=2β−1α.211(11211−1)
⇒25.211=211(11α)(2β−1211−1)
By comparing both sides,
11α=25⇒α=275
and 2β−1211−1=1
⇒211=2β
⇒β=11
∴ α+β=275+11=286