document.write( "Question 1167120: I am given the first three and the last term for this sequence. I need to know the number of terms for this?
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Algebra.Com's Answer #791704 by ikleyn(52794) $\"\"$ $\"About$

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document.write( "Number of terms is the same, as the number of terms in the sequence\r\n" );
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document.write( "    -1, 1, 3, 5, . . . , 19.\r\n" );
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document.write( "Even if you know nothing about arithmetic progressions, and even if you are 2-nd grade student, \r\n" );
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document.write( "you can solve this problem and answer this question by writing all the terms of the sequence in a row and counting them.\r\n" );
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document.write( "But if you are a bit more advanced thinker, you may figure out that the number of gaps between 1 an 19 is\r\n" );
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document.write( "      =  = 9;\r\n" );
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document.write( "Hence, the number of term in the sequence  1, 3, 5, . . . , 19  is  10;\r\n" );
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document.write( "Then joining the term  {-1},  you get that the number under the problem's question is  10 + 1 = 11.    ANSWER\r\n" );
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