document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=892798>Question 892798</A>: <I><SPAN STYLE=\"word-break: break-all;\"> what is the a30 when a1=8000 and r=-1/2\r<BR>\n" );
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document.write( "I had gotten to here ---> 8000(-1/2^30-1)\r<BR>\n" );
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document.write( "I am not getting a clear answer and am getting a very large decimal that does not seem to be right. \r<BR>\n" );
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document.write( "answer gotten ---> -1.86264515E-9  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #540802 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=540802\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A1 = 8000<BR>\n" );
document.write( "An = A1 * r^(n-1)<BR>\n" );
document.write( "r is equal to (-1/2).<BR>\n" );
document.write( "n is equal to 30<BR>\n" );
document.write( "A30 = 8000 * (-1/2)^(30-1) = 8000 * (-1/2)^29 = 8000 * -1.86264515 * 10^-9 which is equal to -1.49011612 * 10^-5.<BR>\n" );
document.write( "that's a very small number.<BR>\n" );
document.write( "pretty close to 0 but not quite.<BR>\n" );
document.write( "it's in scientific notation.<BR>\n" );
document.write( "converting that to decimal notation and the number becomes:<BR>\n" );
document.write( "-.0000149011612.<BR>\n" );
document.write( "the number is very reasonable if you consider that a ratio of (-1/2) means you are dividing 8000 by -2 for 28 times i believe.<BR>\n" );
document.write( "here's the actual individual calculations using excel spreadsheet.<BR>\n" );
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document.write( "your -1.86264515E-9 is correct.<BR>\n" );
document.write( "it means -1.86264515 * 10^-9<BR>\n" );
document.write( "after you multiply that by 8000, you get -1.49011612 * 10^-5.<BR>\n" );
document.write( "that's the value of A30.\r<BR>\n" );
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document.write( "the numbers are good.<BR>\n" );
document.write( "maybe you didn't know they were in scientific format?<BR>\n" );
document.write( "there are a lot of decimal places but the number is very small because the exponent part is -9 for the factor and -5 for the final answer which is the factor * 8000.\r<BR>\n" );
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