Given,
The ratio of the fifth term from the beginning to the fifth term from the end in the binomial expansion of (42+431)n in the increasing powers of 431 be 46:1
Now according to given data we have,
Tn−3T5=Cn−4n(21/4)4(3−1/4)n−4C4n(21/4)n−4(3−1/4)4=146
⇒24n−834n−8=61/4
⇒6n−8=6
⇒n−8=1⇒n=9
So, T6=C59(21/4)4(3−1/4)5=4384
Now comparing with T6=43α,
We get α=84