document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1144193>Question 1144193</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 37\r<BR>\n" );
document.write( "\n" );
document.write( " minutes of calls is $15.42\r<BR>\n" );
document.write( "\n" );
document.write( " and the monthly cost for 53\r<BR>\n" );
document.write( "\n" );
document.write( " minutes is $17.18\r<BR>\n" );
document.write( "\n" );
document.write( ". What is the monthly cost for 39\r<BR>\n" );
document.write( "\n" );
document.write( " minutes of calls? <BR>\n" );
document.write( "   <BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #765218 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=765218\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> linear function is y = mx + b in slope intercept form.<BR>\n" );
document.write( "m is the slope<BR>\n" );
document.write( "b is the y-intercept<BR>\n" );
document.write( "the slope is the change in y divided by the corresponding change in x.<BR>\n" );
document.write( "the y-intercept is the value of y when x = 0.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "37 minutes = $15.42<BR>\n" );
document.write( "53 minutes = $17.18\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "x is the minutes<BR>\n" );
document.write( "y is the cost.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you have two points to consider.<BR>\n" );
document.write( "they are (x1,y1) = (37,15.42) and (x2,y2) = 53,17.18)\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the change in y is 17.18 - 15.42 = 1.76.<BR>\n" );
document.write( "the corresponding change in x is 53 - 37 = 16.<BR>\n" );
document.write( "the slope is 1.76 . 16 = .11\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "y = mx + b becomes y = .11 * x + b<BR>\n" );
document.write( "replace x and y with either one of the coordinate points to solve for b.<BR>\n" );
document.write( "i chose (37,15.42).<BR>\n" );
document.write( "the equation becomes 15.42 = .11 * 37 + b.<BR>\n" );
document.write( "solve for b to get b = 15.42 - .11 * 37 = 15.42 - 11.35\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "your equation becomes y = .11 * x + 11.35\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "when x = 0, y = 11.35<BR>\n" );
document.write( "when x  = 37, y = .11 * 37 + 11.35 = 15.42<BR>\n" );
document.write( "when x = 53, y = .11 * 53 + 11.35 = 17.18\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the equation looks good.<BR>\n" );
document.write( "for 39 minutes, the total cost will be .11 * 39 + 11.35 = $15.64.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "the equation can be graphed.<BR>\n" );
document.write( "the equation to be graphed is y = .11 * x + 11.35<BR>\n" );
document.write( "here's what the graph looks like.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" src = \"http://theo.x10hosting.com/2019/082501.jpg\" alt=\"$$$\" >\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );