document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=55055>Question 55055</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi, the question i have is that a computer is purchased at end of 1999 for $3000.  Scrap value of the computer in 2001 is expected to be $500.  Find a linear function that describes the value of the computer, if t is the age of the computer in years.<BR>\n" );
document.write( "I wouldn't know where to start!!  thanks. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #37294 by </B><A HREF=/tutors/aboutme.mpl?userid=Hook><B>Hook(36)</B></A><img src=\"/images/stars/stars-07.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Hook><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=37294\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The problem asks you to find a linear funtion: let's call it <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=f%28t%29 ALIGN=MIDDLE  ALT=\"f%28t%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "We know its a line, so it can be of the form <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=f%28t%29=mt%2Bb ALIGN=MIDDLE  ALT=\"f%28t%29=mt%2Bb\"   DISABLED_style= \"max-width:90%; height:auto;\" > (That's slope-intercept form there). \r<BR>\n" );
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document.write( "What do we know? <BR>\n" );
document.write( "We're calling <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t ALIGN=MIDDLE  ALT=\"t\"   DISABLED_style= \"max-width:90%; height:auto;\" > the age of the computer. In '99, we're at <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=0 ALIGN=MIDDLE  ALT=\"t=0\"   DISABLED_style= \"max-width:90%; height:auto;\" > and the computer is worth $3000; in '01 <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t=2 ALIGN=MIDDLE  ALT=\"t=2\"   DISABLED_style= \"max-width:90%; height:auto;\" >, the computer is worth $500.\r<BR>\n" );
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document.write( "Ok, so we have these two points:<BR>\n" );
document.write( "(0,3000)<BR>\n" );
document.write( "(2,500)\r<BR>\n" );
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document.write( "Let's plug the first point into that slope-intercept form of our line:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3000=m%280%29%2Bb ALIGN=MIDDLE  ALT=\"3000=m%280%29%2Bb\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The m term drops away and we're simply left with <BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3000+=+b ALIGN=MIDDLE  ALT=\"3000+=+b\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Great. Now lets plug the second point into our equation (we know b now as well)\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=500+=+m%282%29+%2B+3000 ALIGN=MIDDLE  ALT=\"500+=+m%282%29+%2B+3000\"   DISABLED_style= \"max-width:90%; height:auto;\" >}<BR>\n" );
document.write( "If we subtract 3000 from both sides, we get<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-2500+=+2m ALIGN=MIDDLE  ALT=\"-2500+=+2m\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and divide by 2<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-1250+=+m ALIGN=MIDDLE  ALT=\"-1250+=+m\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Throw it all together, we get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=f%28t%29+=+-1250%2At%2B3000 ALIGN=MIDDLE  ALT=\"f%28t%29+=+-1250%2At%2B3000\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "We can eve graph it:\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28300%2C200%2C+-1%2C4%2C-1000%2C4000%2C+-1250%2Ax%2B3000%29 ALIGN=MIDDLE  ALT=\"graph%28300%2C200%2C+-1%2C4%2C-1000%2C4000%2C+-1250%2Ax%2B3000%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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