Let m and n be the coefficients of seventh and thirteenth terms respectively in the expansion of (13x13+12x23)18. Then (nm)13 is: [2024]
19
14
49
94
(4)
Tr+1=Cr18(13x1/3)18-r·(12x-2/3)r
∴ Coefficient of 7th term =C618(13)12·(12)6
and coefficient of 13th term =C1218(13)6·(12)12
So, (nm)1/3=[C1218(13)6·(12)12C618(13)12·(12)6]1/3=94