document.write( "Question 484136: have one question left on a summer packet, not sure how to answer. need to sketch both equations on the same x-y plane..company A offers a cell phone fee of $90/mnth...company B costs $15per month for service and $.10 per minute...need to compare the 2 plans ??????????????????? \n" ); document.write( "
Algebra.Com's Answer #331257 by Theo(13342)\"\" \"About 
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company A charges $90.00 per month flat fee.
\n" ); document.write( "company B charges $15.00 pr month plus $.10 per minute.
\n" ); document.write( "equation for company A is:
\n" ); document.write( "y = 90
\n" ); document.write( "equation for company B is:
\n" ); document.write( "y = .10*x + 15
\n" ); document.write( "you can graph both equations.
\n" ); document.write( "looks like this:
\n" ); document.write( "\"graph%28400%2C400%2C-100%2C1000%2C-10%2C100%2C90%2C.10x%2B15%29\"
\n" ); document.write( "the plan with the flat rate is more expensive up to about x minutes.
\n" ); document.write( "you can solve for the exact value by solving the 2 equations simultaneously.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "the 2 equations are:
\n" ); document.write( "y = 90
\n" ); document.write( "y = .10x + 15
\n" ); document.write( "since they both equal to y, then set them equal to each other to get:
\n" ); document.write( "90 = .10x + 15
\n" ); document.write( "subtract 15 from both sides of the equation to get:
\n" ); document.write( "75 = .10x
\n" ); document.write( "divide both sides of the equation by .10 to get:
\n" ); document.write( "x = 750
\n" ); document.write( "the break even point is at 750 minutes.
\n" ); document.write( "the graph has been modified to provide a horizontal line at y = 90 and a vertical line at x = 750.
\n" ); document.write( "the intersection of the horizontal line and the vertical line should be the break even point.
\n" ); document.write( "\"graph%28400%2C400%2C-100%2C1000%2C-10%2C100%2C90%2C.10x%2B15%2C10%2A%28x-750%29%29\"
\n" ); document.write( "the horizontal line at y = 90 is the equation for Company A.
\n" ); document.write( "The slanted line is the equation for Company B.
\n" ); document.write( "It intercepts the y axis at x = 15 which is the cost to the customer with 0 minutes used.
\n" ); document.write( "The vertical line shows you that the intersection of the graph of the equation for Company A and the graph of the equation for Company B occurs at x = 750 which is the break even point.
\n" ); document.write( "the value of x in the graph is the number of minutes used.
\n" ); document.write( "the value of y in the graph is the cost for the number of minutes used.
\n" ); document.write( "you can see that the cost for company A customer is $90.00 regardless of the number of minutes they used, while the cost for company B customer has a fixed component ($15.00) and a variable component (10 cents a minute).\r
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