Saved Bookmarks
| 1. |
n!/(n-r)!r!+n!/(n-r+1)!(r-1)!=?? |
| Answer» Ans:(n+1)! / r! ( n-r+1)!\xa0\xa0To proven! / r!(n-r)! + n! / (r-1)! (n-r+1)! = (n+1)! / r!(n-r+1)!L.H.Sn! / (r)(r-1)! (n-r)! +n! / (r-1)! (n-r+1)(n-r)!n! / (r-1)! (n-r)! will be commonso,n! / (r-1)! (n-r)! *[ 1/r + 1/(n-r+1) ]n! / (r-1)! (n-r)! *[ n-r+1+r / nr-r2\xa0+r ]we will get ,n! / (r-1)! (n-r)! / * [n+1 / r(n-r+1)](n!) (n+1) / (r-1)! (r) (n-r)! (n-r+1)(n+1)! / r! ( n-r+1)! | |