document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=113214>Question 113214</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Homework problem: The formula N=4x^2+5x+1 represents the number of househoulds N, in thousands, in a certain city that has a computer x years after 1990. According to the formula, in what year were there 175 thousand households with computers in this city? I would like to see how this is worked out, not just get an answer. Thank you! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #82392 by </B><A HREF=/tutors/aboutme.mpl?userid=solver91311><B>solver91311(24713)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=solver91311><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=solver91311><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=82392\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=N=4x%5E2%2B5x%2B1 ALIGN=MIDDLE  ALT=\"N=4x%5E2%2B5x%2B1\"   DISABLED_style= \"max-width:90%; height:auto;\" > is the given function.  We want to know x when N = 175.  So,\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x%5E2%2B5x%2B1=175 ALIGN=MIDDLE  ALT=\"4x%5E2%2B5x%2B1=175\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x%5E2%2B5x%2B1-175=0 ALIGN=MIDDLE  ALT=\"4x%5E2%2B5x%2B1-175=0\"   DISABLED_style= \"max-width:90%; height:auto;\" >, subtract 175 from both sides<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x%5E2%2B5x-174=0 ALIGN=MIDDLE  ALT=\"4x%5E2%2B5x-174=0\"   DISABLED_style= \"max-width:90%; height:auto;\" >, collect terms\r<BR>\n" );
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document.write( "As it happens, this trinomial is factorable:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x%5E2%2B5x-174=%284x%2B29%29%28x-6%29 ALIGN=MIDDLE  ALT=\"4x%5E2%2B5x-174=%284x%2B29%29%28x-6%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >, so<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%284x%2B29%29%28x-6%29=0 ALIGN=MIDDLE  ALT=\"%284x%2B29%29%28x-6%29=0\"   DISABLED_style= \"max-width:90%; height:auto;\" >, and \r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=6 ALIGN=MIDDLE  ALT=\"x=6\"   DISABLED_style= \"max-width:90%; height:auto;\" > or<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=-29%2F4 ALIGN=MIDDLE  ALT=\"x=-29%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "A negative number of years in this case would be absurd, so you can exclude the negative result.  The answer is 6 years.\r<BR>\n" );
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document.write( "Hope this helps,<BR>\n" );
document.write( "John<BR>\n" );
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