document.write( "Question 1002016: Write the following expression without using the factorial symbol.\r
\n" ); document.write( "\n" ); document.write( "nC3 + nC2 + nC1\r
\n" ); document.write( "\n" ); document.write( "The formula given is n!/r!(n-r)!.
\n" ); document.write( "My teacher was saying the answer is n^3 + 5n/6.
\n" ); document.write( "Im very curious as to how the question is written in each step. I have tried many times to get an answer similiar to this. Thank you so much in advance!! \n" ); document.write( "

Algebra.Com's Answer #619052 by Boreal(15235) $\"\"$ $\"About$

You can put this solution on YOUR website!
n!/(n-3)!3!=n(n-1)(n-2)/6; n(n-1)(n-2)=(n^2-n)(n-2)=(n^3-3n^2+2n)/6
\n" ); document.write( "n!/(n-2)!2!=n(n-1)/2
\n" ); document.write( "n
\n" ); document.write( "n+(n^2-n)/2+(n^3-3n^2+2n)/6=
\n" ); document.write( "multiply everything by (6/6)=1
\n" ); document.write( "(6n+3n^2-3n+n^3-3n^2+2n)/6
\n" ); document.write( "(n^3+5n)/6 \n" ); document.write( "

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