document.write( "Question 82170: This is the first time I need help bad and using this. I have to write an equation that models between time and distance using this chart.\r
\n" ); document.write( "\n" ); document.write( "on the chart (time[seconds]=distance) 1=1100 2=2200 3=3300 4=4400 5=5500
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\n" ); document.write( "\n" ); document.write( "Also, i need help with this problem.\r
\n" ); document.write( "\n" ); document.write( "What number of hours are the two plans equal?
\n" ); document.write( "Plan A; $20 per hour
\n" ); document.write( "Plan B: $8 per hour + $12\r
\n" ); document.write( "\n" ); document.write( "If you can help me thank you very much!
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Algebra.Com's Answer #58868 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let x=time, y=distance\r
\n" ); document.write( "\n" ); document.write( "Since we have a relationship between the time and distances, we can say that these times and distances follow a pattern. We can find the formula for this pattern by letting x=1 second and y=1100 to get one point (1,1100). Now let x=2 and y=2200. Now that we have 2 points (1,1100) and (2,2200) and we can now make a line\r
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Solved by pluggable solver: Finding the Equation of a Line
First lets find the slope through the points (\"1\",\"1100\") and (\"2\",\"2200\")
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\n" ); document.write( " \"m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29\" Start with the slope formula (note: (\"x%5B1%5D\",\"y%5B1%5D\") is the first point (\"1\",\"1100\") and (\"x%5B2%5D\",\"y%5B2%5D\") is the second point (\"2\",\"2200\"))
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\n" ); document.write( " \"m=%282200-1100%29%2F%282-1%29\" Plug in \"y%5B2%5D=2200\",\"y%5B1%5D=1100\",\"x%5B2%5D=2\",\"x%5B1%5D=1\" (these are the coordinates of given points)
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\n" ); document.write( " \"m=+1100%2F1\" Subtract the terms in the numerator \"2200-1100\" to get \"1100\". Subtract the terms in the denominator \"2-1\" to get \"1\"
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\n" ); document.write( " So the slope is
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\n" ); document.write( " \"m=1100\"
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\n" ); document.write( "Now let's use the point-slope formula to find the equation of the line:
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\n" ); document.write( " ------Point-Slope Formula------
\n" ); document.write( " \"y-y%5B1%5D=m%28x-x%5B1%5D%29\" where \"m\" is the slope, and (\"x%5B1%5D\",\"y%5B1%5D\") is one of the given points
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\n" ); document.write( " So lets use the Point-Slope Formula to find the equation of the line
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\n" ); document.write( " \"y-1100=%281100%29%28x-1%29\" Plug in \"m=1100\", \"x%5B1%5D=1\", and \"y%5B1%5D=1100\" (these values are given)
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\n" ); document.write( " \"y-1100=1100x%2B%281100%29%28-1%29\" Distribute \"1100\"
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\n" ); document.write( " \"y-1100=1100x-1100\" Multiply \"1100\" and \"-1\" to get \"-1100%2F1\". Now reduce \"-1100%2F1\" to get \"-1100\"
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\n" ); document.write( " \"y=1100x-1100%2B1100\" Add \"1100\" to both sides to isolate y
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\n" ); document.write( " \"y=1100x%2B0\" Combine like terms \"-1100\" and \"1100\" to get \"0\"
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\n" ); document.write( " Answer:
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\n" ); document.write( " So the equation of the line which goes through the points (\"1\",\"1100\") and (\"2\",\"2200\") is:\"y=1100x%2B0\"
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\n" ); document.write( " The equation is now in \"y=mx%2Bb\" form (which is slope-intercept form) where the slope is \"m=1100\" and the y-intercept is \"b=0\"
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\n" ); document.write( " Notice if we graph the equation \"y=1100x%2B0\" and plot the points (\"1\",\"1100\") and (\"2\",\"2200\"), we get this: (note: if you need help with graphing, check out this solver)
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\n" ); document.write( " Graph of \"y=1100x%2B0\" through the points (\"1\",\"1100\") and (\"2\",\"2200\")
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\n" ); document.write( " Notice how the two points lie on the line. This graphically verifies our answer.
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\n" ); document.write( "\n" ); document.write( "So we can see that equation is \"y=1100x\". We can check this by plugging in x=1 to get\r
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\n" ); document.write( "\n" ); document.write( "\"y=1100%281%29\" Plug in x=1\r
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\n" ); document.write( "\n" ); document.write( "\"y=1100\" works\r
\n" ); document.write( "\n" ); document.write( "And we can do this for every x to verify.\r
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\n" ); document.write( "\n" ); document.write( "For the second problem, we're going to make equations of the two plans and find out where they intersect:\r
\n" ); document.write( "\n" ); document.write( "So $20 an hour translates to this equation:\r
\n" ); document.write( "\n" ); document.write( "\"y=20x\"\r
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\n" ); document.write( "\n" ); document.write( "and $8 per hour + $12 translates to:\r
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\n" ); document.write( "\n" ); document.write( "\"y=8x%2B12\"\r
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\n" ); document.write( "\n" ); document.write( "So now set them equal to each other to see when the plans will be the same\r
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\n" ); document.write( "\n" ); document.write( "\"20x=8x%2B12\"\r
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\n" ); document.write( "\n" ); document.write( "\"20x-8x=cross%288x-8x%29%2B12\" Subtract 8x from both sides\r
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\n" ); document.write( "\n" ); document.write( "\"12x=12\"\r
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\n" ); document.write( "\n" ); document.write( "\"cross%2812%2F12%29x=12%2F12\" Divide both sides by 12\r
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\n" ); document.write( "\n" ); document.write( "\"x=1\" \r
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\n" ); document.write( "\n" ); document.write( "So the plans are equal at x=1, which is 1 hour.
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