Tr+1=Cr10(αx91)10−r(βx−61)r
Tr+1=Cr10α10−rβr(x)910−r−6r
Term independent of x⇒Power of x=0
910−r−6r=0⇒r=4
T5=C410α6β4
Now Let α3,β2 are two numbers. Clearly both are positive.
A.M.≥G.M.
⇒2α3+β2≥(α3β2)1/2
⇒α3β2≤4
⇒α6β4≤16
⇒10C4T5≤16
⇒T5≤16.10C4
⇒T5max=16×10C4=10k
⇒10k=3360
⇒k=336