document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=214899>Question 214899</A>: <I><SPAN STYLE=\"word-break: break-all;\"> This question I come up with the wrong answer:<BR>\n" );
document.write( "Pete drove from Buffalo to Boston, a distance of 720km. On return trip he increased his speed by 10km/h.  If the total trip took 17h, what was his speed from Boston to Buffalo?\r<BR>\n" );
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document.write( "I'm having trouble working it out, I begin with this:\r<BR>\n" );
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document.write( "I start with (720/x)+(720/x+10)\r<BR>\n" );
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document.write( "Expanded it to: 17x^2 - 1270x + 7200\r<BR>\n" );
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document.write( "Speed I got next using the quadratic equation: 62.5\r<BR>\n" );
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document.write( "But thats apparently wrong, what am I doing wrong? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #162354 by </B><A HREF=/tutors/aboutme.mpl?userid=josmiceli><B>josmiceli(19441)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josmiceli><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=josmiceli><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=162354\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I write 2 equations, 1 for each<BR>\n" );
document.write( "leg of the trip.<BR>\n" );
document.write( "Buffalo to Boston:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%5B1%5D+=+r%5B1%5D%2At%5B1%5D ALIGN=MIDDLE  ALT=\"d%5B1%5D+=+r%5B1%5D%2At%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%5B2%5D+=+r%5B2%5D%2At%5B2%5D ALIGN=MIDDLE  ALT=\"d%5B2%5D+=+r%5B2%5D%2At%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "given:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%5B1%5D+=+720 ALIGN=MIDDLE  ALT=\"d%5B1%5D+=+720\"   DISABLED_style= \"max-width:90%; height:auto;\" > km<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d%5B2%5D+=+720 ALIGN=MIDDLE  ALT=\"d%5B2%5D+=+720\"   DISABLED_style= \"max-width:90%; height:auto;\" > km<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D+=+r%5B1%5D+%2B+10 ALIGN=MIDDLE  ALT=\"r%5B2%5D+=+r%5B1%5D+%2B+10\"   DISABLED_style= \"max-width:90%; height:auto;\" > km/hr<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B1%5D+%2B+t%5B2%5D+=+17 ALIGN=MIDDLE  ALT=\"t%5B1%5D+%2B+t%5B2%5D+=+17\"   DISABLED_style= \"max-width:90%; height:auto;\" > Hr<BR>\n" );
document.write( "-----------------------<BR>\n" );
document.write( "I can rewrite the equations<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+r%5B1%5D%2At%5B1%5D ALIGN=MIDDLE  ALT=\"720+=+r%5B1%5D%2At%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B1%5D+=+720%2Fr%5B1%5D ALIGN=MIDDLE  ALT=\"t%5B1%5D+=+720%2Fr%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+%28r%5B1%5D+%2B+10%29%2At%5B2%5D ALIGN=MIDDLE  ALT=\"720+=+%28r%5B1%5D+%2B+10%29%2At%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+%28r%5B1%5D+%2B+10%29%2A%2817+-+t%5B1%5D%29 ALIGN=MIDDLE  ALT=\"720+=+%28r%5B1%5D+%2B+10%29%2A%2817+-+t%5B1%5D%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+17r%5B1%5D+%2B+170+-+r%5B1%5Dt%5B1%5D+-+10t%5B1%5D ALIGN=MIDDLE  ALT=\"720+=+17r%5B1%5D+%2B+170+-+r%5B1%5Dt%5B1%5D+-+10t%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "By substitution:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+17r%5B1%5D+%2B+170+-+720+-+10t%5B1%5D ALIGN=MIDDLE  ALT=\"720+=+17r%5B1%5D+%2B+170+-+720+-+10t%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+%2B+550+=+17r%5B1%5D+-+10%2A%28720%2Fr%5B1%5D%29 ALIGN=MIDDLE  ALT=\"720+%2B+550+=+17r%5B1%5D+-+10%2A%28720%2Fr%5B1%5D%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Multiply both sides by <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D ALIGN=MIDDLE  ALT=\"r%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1270r%5B1%5D+=+17%2A%28r%5B1%5D%29%5E2+-+7200 ALIGN=MIDDLE  ALT=\"1270r%5B1%5D+=+17%2A%28r%5B1%5D%29%5E2+-+7200\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=17%2A%28r%5B1%5D%5E2%29+-+1270r%5B1%5D+-+7200+=+0 ALIGN=MIDDLE  ALT=\"17%2A%28r%5B1%5D%5E2%29+-+1270r%5B1%5D+-+7200+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Using quadratic equation:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a+=+17 ALIGN=MIDDLE  ALT=\"a+=+17\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b+=+-1270 ALIGN=MIDDLE  ALT=\"b+=+-1270\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=c+=+-7200 ALIGN=MIDDLE  ALT=\"c+=+-7200\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+%28-%28-1270%29+%2B-+sqrt%28+%28-1270%29%5E2-4%2A17%2A%28-7200%29+%29%29%2F%282%2A17%29+ ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+%28+1270+%2B-+sqrt%28+1612900+%2B+489600+%29%29%2F+34+ ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+%28+1270+%2B-+sqrt%28+1612900+%2B+489600+%29%29%2F+34+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+%28+1270+%2B-+sqrt%28+2102500+%29%29%2F+34+ ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+%28+1270+%2B-+sqrt%28+2102500+%29%29%2F+34+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+%28+1270+%2B-+1450%29%2F+34+ ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+%28+1270+%2B-+1450%29%2F+34+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+2720%2F34 ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+2720%2F34\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+80 ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+80\"   DISABLED_style= \"max-width:90%; height:auto;\" > km/hr<BR>\n" );
document.write( "His speed from Buffalo to Boston was 80 km/hr<BR>\n" );
document.write( "check:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D+=+r%5B1%5D+%2B+10 ALIGN=MIDDLE  ALT=\"r%5B2%5D+=+r%5B1%5D+%2B+10\"   DISABLED_style= \"max-width:90%; height:auto;\" > km/hr<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D+=+90 ALIGN=MIDDLE  ALT=\"r%5B2%5D+=+90\"   DISABLED_style= \"max-width:90%; height:auto;\" > km/hr<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+r%5B1%5D%2At%5B1%5D ALIGN=MIDDLE  ALT=\"720+=+r%5B1%5D%2At%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+80%2At%5B1%5D ALIGN=MIDDLE  ALT=\"720+=+80%2At%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B1%5D+=+9 ALIGN=MIDDLE  ALT=\"t%5B1%5D+=+9\"   DISABLED_style= \"max-width:90%; height:auto;\" > hr<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B2%5D+=+17+-+9 ALIGN=MIDDLE  ALT=\"t%5B2%5D+=+17+-+9\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B2%5D+=+8 ALIGN=MIDDLE  ALT=\"t%5B2%5D+=+8\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+90%2A8 ALIGN=MIDDLE  ALT=\"720+=+90%2A8\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=720+=+720 ALIGN=MIDDLE  ALT=\"720+=+720\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "OK<BR>\n" );
document.write( "It looks like you had a sign wrong\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );