document.write( "Question 21401: prove that: nCr=(n/r)(n-1)C(r-1) \n" ); document.write( "

Algebra.Com's Answer #11849 by venugopalramana(3286) $\"\"$ $\"About$

You can put this solution on YOUR website!
LHS=nCr=n!/[(n-r)!r!]
\n" ); document.write( "RHS=(n/r)(n-1)C(r-1)=(n/r)[(n-1)!/{(n-1)-(r-1)}!(r-1)!]
\n" ); document.write( "=[n(n-1)!/{(n-1-r+1)!(r-1)!r]=n!/[(n-r)!r!]=LHS
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