document.write( "Question 622864: First Question: Find the initial term of the arithmetic sequence with 10th term -1 and 20th term 7. (use initial term a0)\r
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\n" ); document.write( "\n" ); document.write( "Second Question: There are two geometric sequences with 2nd term 5 and 4th term 80. What are the two possible values of the 3rd term?\r
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\n" ); document.write( "\n" ); document.write( "I truly appreciate your help!!
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Algebra.Com's Answer #391699 by MathTherapy(10552)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "Using the formula for an arithmetic sequence\"t%5Bn%5D+=+t%5B1%5D+%2B+%28n+-+1%29d\", we get:\r
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\n" ); document.write( "\n" ); document.write( "\"t%5B10%5D+=+t%5B1%5D+%2B+%28n+-+1%29d\"
\n" ); document.write( "\"t%5B10%5D+=+t%5B1%5D+%2B+%2810+-+1%29d\" ----- Substituting 10 for n in formula
\n" ); document.write( "\"-+1+=+t%5B1%5D+%2B+%2810+-+1%29d\"
\n" ); document.write( "\"-+1+=+t%5B1%5D+%2B+9d\"
\n" ); document.write( "\"t%5B1%5D+%2B+9d+=+-+1\" ---- eq (i)\r
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\n" ); document.write( "\n" ); document.write( "\"t%5Bn%5D+=+t%5B1%5D+%2B+%28n+-+1%29d\"
\n" ); document.write( "\"t%5B20%5D+=+t%5B1%5D+%2B+%2820+-+1%29d\" ----- Substituting 20 for n in formula
\n" ); document.write( "\"7+=+t%5B1%5D+%2B+%2820+-+1%29d\"
\n" ); document.write( "\"7+=+t%5B1%5D+%2B+19d\"
\n" ); document.write( "\"t%5B1%5D+%2B+19d+=+7\" ------ eq (ii)\r
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\n" ); document.write( "\n" ); document.write( "\"t%5B1%5D+%2B+9d+=+-+1\" ---- eq (i)
\n" ); document.write( "\"t%5B1%5D+%2B+19d+=+7\" ---- eq (ii)
\n" ); document.write( "- 10d = - 8 ------ Subtracting eq (ii) from eq (i)
\n" ); document.write( "d, or difference = \"%28-+8%29%2F-+10\", or \"4%2F5\"\r
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\n" ); document.write( "\n" ); document.write( "Since d = \"4%2F5\", then \"t%5Bn%5D+=+t%5B1%5D+%2B+%28n+-+1%29d\" becomes: \"t%5B10%5D+=+t%5B1%5D+%2B+%2810+-+1%29+%2A+%284%2F5%29\" ----- Substituting 10 for n, and \"4%2F5\" for d in formula
\n" ); document.write( "\"-+1+=+t%5B1%5D+%2B+9+%2A+%284%2F5%29\"
\n" ); document.write( "\"-+1+=+t%5B1%5D+%2B+%2836%2F5%29\"
\n" ); document.write( "\"t%5B1%5D+=+-+1+-+%2836%2F5+%29\"
\n" ); document.write( "\"t%5B1%5D+=+-+%285%2F5%29+-+%2836%2F5%29\"
\n" ); document.write( "Initial term, or \"highlight_green%28t%5B1%5D+=+-+%2841%2F5%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "=========
\n" ); document.write( "Check
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\n" ); document.write( "\n" ); document.write( "10th term
\n" ); document.write( "\"t%5Bn%5D+=+t%5B1%5D+%2B+%28n+-+1%29d\"
\n" ); document.write( "\"-+1+=+%28-+41%2F5%29+%2B+%2810+-+1%29+%2A+%284%2F5%29\"
\n" ); document.write( "\"-+1+=+%28-+41%2F5%29+%2B+9+%2A+%284%2F5%29\"
\n" ); document.write( "\"-+1+=+%28-+41%2F5%29+%2B+%2836%2F5%29\"
\n" ); document.write( "\"-+1+=+-+%285%2F5%29\"
\n" ); document.write( "- 1 = - 1 (TRUE)\r
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\n" ); document.write( "\n" ); document.write( "20th term
\n" ); document.write( "\"t%5Bn%5D+=+t%5B1%5D+%2B+%28n+-+1%29d\"
\n" ); document.write( "\"7+=+%28-+41%2F5%29+%2B+%2820+-+1%29+%2A+%284%2F5%29\"
\n" ); document.write( "\"7+=+%28-+41%2F5%29+%2B+19+%2A+%284%2F5%29\"
\n" ); document.write( "\"7+=+%28-+41%2F5%29+%2B+%2876%2F5%29\"
\n" ); document.write( "\"7+=+%2835%2F5%29\"
\n" ); document.write( "7 = 7 (TRUE)\r
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\n" ); document.write( "\n" ); document.write( "Send comments and “thank-yous” to “D” at MathMadEzy@aol.com
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