document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1042615>Question 1042615</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A school record in a certain race in 1960 was 3.8 minutes. In 1980 the school record in the same event was 3.65 minutes.Choose the linear equation for these data points.(y=-.0075x+18.5),(y=.0075x-18.5), (y=.0075x 0.18.5) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #657602 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=657602\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The year is the x-value (fixed, known) and the time for the race the y-value.<BR>\n" );
document.write( "slope is<BR>\n" );
document.write( " change in y/change in x.<BR>\n" );
document.write( "It is 3.65-3.80/1980-1960<BR>\n" );
document.write( "That is -0.15/20= -0.0075<BR>\n" );
document.write( "Now use the point slope formula<BR>\n" );
document.write( "y-y1=m(x-x1)<BR>\n" );
document.write( "y-3.8=-0.0075(x-1960), using the first point (the second will give the same answer)<BR>\n" );
document.write( "y=-.0075x-(-0.0075*1960)+3.8<BR>\n" );
document.write( "y=-0.0075x+14.7+3.8<BR>\n" );
document.write( "y=-0.0075x+18.5, the first ANSWER<BR>\n" );
document.write( "Check using second point.<BR>\n" );
document.write( "y-3.65=-0.0075(x-1980)<BR>\n" );
document.write( "y-3.65=-0.0075x+14.85<BR>\n" );
document.write( "y=-0.0075x+18.5 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );