Q28Fill in the blanks
If the seventh terms from the beginning and the end in the expansion of 3 1 2+ 3 are equal, then n equals _________________ . 1 n−6 6 1 6 n−6 [Hint : T7 = T n – 7 + 2 ⇒ C ( ) 6 23 = C (2 ) 1 n −6 33 33 n − 12 1 n − 12 1 ⇒ ( ) 23 = 1 ⇒ only problem when n – 12 = 0 ⇒ n = 12]. –6 4 1 2b