document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=734136>Question 734136</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A boat travels 7 km upstream and 7km back. The time for the round trip is 10 hours. The speed of the stream is 4 km/hr. What is the speed of the boat in still water? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #448739 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><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=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=448739\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A boat travels 7 km upstream and 7km back. The time for the round trip is 10 hours. The speed of the stream is 4 km/hr. What is the speed of the boat in still water?\r<BR>\n" );
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document.write( "let speed in still water = x km/h\r<BR>\n" );
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document.write( "with current x+4 km/h\r<BR>\n" );
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document.write( "against current speed = x-4 km/h\r<BR>\n" );
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document.write( "time up + time return = 10\r<BR>\n" );
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document.write( "7/(x+4)+7/(x-4)=10\r<BR>\n" );
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document.write( "multiply equation by (x+4)(x-4)\r<BR>\n" );
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document.write( "7(x-4)+7(x+4)= 10(x^2-16)\r<BR>\n" );
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document.write( "7x-28+7x+28 = 10x^2-160\r<BR>\n" );
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document.write( "14x=10x^2-160\r<BR>\n" );
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document.write( "10x^2-14x-160=0\r<BR>\n" );
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document.write( "/2<BR>\n" );
document.write( "5x^2-7x-80=0\r<BR>\n" );
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document.write( "Find the roots of the equation by quadratic formula								<BR>\n" );
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document.write( "a=	5	,	b=	-7	,	c=	-80	<BR>\n" );
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document.write( "b^2-4ac=	49	+	1600					<BR>\n" );
document.write( "b^2-4ac=	1649							<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%09sqrt%28%091649%09%29=%0940.61%09 ALIGN=MIDDLE  ALT=\"%09sqrt%28%091649%09%29=%0940.61%09\"   DISABLED_style= \"max-width:90%; height:auto;\" >			<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29 ALIGN=MIDDLE  ALT=\"x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >								<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29 ALIGN=MIDDLE  ALT=\"x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >								<BR>\n" );
document.write( "x1=(	7	+	40.61	)/	10			<BR>\n" );
document.write( "x1=	4.76							<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x2=%28-b-sqrt%28b%5E2-4ac%29%29%2F%282a%29 ALIGN=MIDDLE  ALT=\"x2=%28-b-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >								<BR>\n" );
document.write( "x2=(	7	-40.61	) /	10				<BR>\n" );
document.write( "x2=	-3.36							<BR>\n" );
document.write( "Ignore negative value								<BR>\n" );
document.write( "boat   	speed	4.761	kph					\r<BR>\n" );
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document.write( " </SPAN>\n" );
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