document.write( "Question 1107560: Bridget's classroom started out with a collection of only 6 books, but she plans to purchase an additional 3 books per week. Cole's library started out with 38 books, and he will purchase another 1 book per week. At what week and amount of books will the two libraries be the same? \n" ); document.write( "
Algebra.Com's Answer #843411 by mccravyedwin(407)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "If you are studying arithmetic sequences (progressions), this is the way\r\n" );
document.write( "you should do it.\r\n" );
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document.write( "Bridget's is an arithmetic sequence (progression) with a1=6+3=9 and d=3.\r\n" );
document.write( "So her number of books on the nth week is \r\n" );
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document.write( "\"a%5Bn%5D=a%5B1%5D%2B%28n-1%29d\"\r\n" );
document.write( "\"a%5Bn%5D=9%2B%28n-1%29%2A3\"\r\n" );
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document.write( "Cole's is an arithmetic sequence with a1=38+1=39 and d=1.\r\n" );
document.write( "So his number of books on the nth week is\r\n" );
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document.write( "\"a%5Bn%5D=a%5B1%5D%2B%28n-1%29d\"\r\n" );
document.write( "\"a%5Bn%5D=39%2B%28n-1%291\"\r\n" );
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document.write( "Set them equal:\r\n" );
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document.write( "\"9%2B%28n-1%293\"\"%22%22=%22%22\"\"39%2B%28n-1%291\"\r\n" );
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document.write( "Simplify and solve for n.  You'll get 16 weeks.\r\n" );
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document.write( "Edwin
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