Most Important Selected Qs for JEE AdvancedMathematicsBinomial Theorem
The value of _ n _ r=1 ^n ( _ t=0 ^ r-1 1 5^n ^n C_r ^r C_t 3^t ) is equal to
Options
- A4
- B3
- C1
- Dnone of these
Correct answer
C. 1
Step-by-step solution
_ n _ r=1 ^n 1 5^n ^n C_r ( _ t=0 ^ r-1 ^r C_t 3^t )= _ n _ r=1 ^n 1 5^n ^n C_r (4^r-3^r )= _ n 1 5^n ( _ r=1 ^n ^n C_r 4^r- _ r=1 ^n ^n C_r 3^r )= _ n 1 5^n (5^n-4^n )=1