I have to prove that
n+1 choose k = n choose k + n choose k-1
Where on earth do I start? Any help much appreciated!
Hello, eliz1906!
It takes only algebra . . . a lot of it!
Prove: .
The right side is: .
Get a common denominator:
. . . .
Factor: .
Reduce: .
. . . . . .
. . . . . .
. . . . . .
Edit: Ah, Archie beat me to it!
. . . .But I'm not deleting all this work . . . So there!
.