NTA Abhyas JEE Main2020MathematicsBinomial TheoremPractice
The number of integral terms in the expansion of 5 1 6 + 7 1 9 1824 is
Options
- A84
- B96
- C91
- D102
Correct answer
D. 102
Step-by-step solution
T r + 1 = 1824 C r 5 1 6 1824 - r 7 1 9 r = 1824 C r 5 1824 - r 6 7 r 9 = 1824 C r 5 304 - r 6 7 r 9 Both r 6 and r 9 are integers, if r is a multiple of 18 ⇒ r = 0,18,36 , . . . . . . , 181 8 Let, the number of terms be n ⇒ 1818 = 0 + n - 1 18 ⇒ n = 102 .