document.write( "Question 947547: nCr/nCr-1 = (n-r+1)/r
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Algebra.Com's Answer #578271 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "To prove:\r\n" );
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document.write( "\"nCr%2FnC%28r-1%29\"\"%22%22=%22%22\"\"%28n-r%2B1%29%2Fr\"\r\n" );
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document.write( "We begin with the left side and we show that\r\n" );
document.write( "it equals the right side:\r\n" );
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document.write( "\"nCr%2FnC%28r-1%29\"\r\n" );
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document.write( "\"nCr\"\"%22%F7%22\"\"nC%28r-1%29\"\r\n" );
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document.write( "\"n%21%2F%28r%21%28n-r%29%21%29\"\"%22%F7%22\"\"n%21%2F%28%28r-1%29%21%28n%5E%22%22-%28r-1%29%29%21+%29\"\r\n" );
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document.write( "\"n%21%2F%28r%21%28n-r%29%21%29\"\"%22%F7%22\"\"n%21%2F%28%28r-1%29%21%28n-r%2B1%29%21+%29\"\r\n" );
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document.write( "\"n%21%2F%28r%21%28n-r%29%21%29\"\"%22%D7%22\"\"%28%28r-1%29%21%28n-r%2B1%29%21+%29%2Fn%21\"\r\n" );
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document.write( "\"cross%28n%21%29%2F%28r%21%28n-r%29%21%29\"\"%22%D7%22\"\"%28%28r-1%29%21%28n-r%2B1%29%21+%29%2Fcross%28n%21%29\"\r\n" );
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document.write( "\"%28r-1%29%21%28n-r%2B1%29%21%2F%28r%21%2A%28n-r%29%21%29\"\r\n" );
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document.write( "Write (n-r+1)! as (n-r+1)(n-r)! and r! as r(r-1)!\r\n" );
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document.write( "\"%28%28r-1%29%21%28n-r%2B1%29%28n-r%29%21%29%2F%28r%2A%28r-1%29%21%2A%28n-r%29%21%29\"\r\n" );
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document.write( "\"%28n-r%2B1%29%2Fr\"\r\n" );
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document.write( "Edwin
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