document.write( "Question 1081850: Can you please help me evaluate these two expressions? Thank you.
\n" ); document.write( "expression 1 = ₉C₂
\n" ); document.write( "expression 2 = ₇₀C₃
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Algebra.Com's Answer #695902 by math_helper(2461)\"\" \"About 
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nCr = n!/((n-r)!*r!) (\"Combinations\" or ways to arrange objects when order doesn't matter)
\n" ); document.write( "where:
\n" ); document.write( " n! = n*(n-1)*(n-2)*…*3*2*1 (I leave off the *1 when solving problems, it doesn't change anything)\r
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\n" ); document.write( "Expression 1:
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\n" ); document.write( "\n" ); document.write( "Because I've seen these before, if I were writing it out, I'd say to myself 9*8 (because 7, 6, …, 2 will cancel from the (9-2)! = 7! part), divided by 2!=2:
\n" ); document.write( "\"+9C2+=+9%2A8%2F2%21+=+36+\"
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\n" ); document.write( "\n" ); document.write( "For expression 2, using the shortcut, \"+70C3+=+70%21%2F%28%2867%21%29%2A%283%21%29%29+=+%2870%2A69%2A68%29%2F%283%2A2%29+=+54740+\"
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