AP EAMCET202017 Sep 2020Evening ShiftMathematicsPermutation and CombinationActual
If (n ) is a positive integer, then ( _ r=1 ^n r C_r= )
Options
- A(2^ n-1 )
- B(n 2^ n-1 )
- C(n 2^ n+1 )
- D(2^ n+1 )
Correct answer
B. (n 2^ n-1 )
Step-by-step solution
( _ r=1 ^n r C_r ) (=1 C₁+2 C₂+3 C₃+ + +n C_n=n 2^ n-1 )