document.write( "Question 199578: Solve the sytem of equations by graphing. Then classify the system.
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Algebra.Com's Answer #149979 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Start with the given system of equations:\r
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\n" ); document.write( "\n" ); document.write( "\"system%28x%2By=15%2Cx-y=3%29\"\r
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\n" ); document.write( "\n" ); document.write( "In order to graph these equations, we must solve for y first.\r
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\n" ); document.write( "\n" ); document.write( "Let's graph the first equation:\r
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\n" ); document.write( "\n" ); document.write( "\"x%2By=15\" Start with the first equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=15-x\" Subtract \"x\" from both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-x%2B15\" Rearrange the terms and simplify.\r
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\n" ); document.write( "\n" ); document.write( "Looking at \"y=-x%2B15\" we can see that the equation is in slope-intercept form \"y=mx%2Bb\" where the slope is \"m=-1\" and the y-intercept is \"b=15\" \r
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\n" ); document.write( "\n" ); document.write( "Since \"b=15\" this tells us that the y-intercept is .Remember the y-intercept is the point where the graph intersects with the y-axis\r
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\n" ); document.write( "\n" ); document.write( "So we have one point \r
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\n" ); document.write( "\n" ); document.write( "Now since the slope is comprised of the \"rise\" over the \"run\" this means\r
\n" ); document.write( "\n" ); document.write( "\"slope=rise%2Frun\"\r
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\n" ); document.write( "\n" ); document.write( "Also, because the slope is \"-1\", this means:\r
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\n" ); document.write( "\n" ); document.write( "\"rise%2Frun=-1%2F1\"\r
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\n" ); document.write( "\n" ); document.write( "which shows us that the rise is -1 and the run is 1. This means that to go from point to point, we can go down 1 and over 1\r
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\n" ); document.write( "\n" ); document.write( "So starting at , go down 1 unit \r
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\n" ); document.write( "\n" ); document.write( "and to the right 1 unit to get to the next point \r
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\n" ); document.write( "\n" ); document.write( "Now draw a line through these points to graph \"y=-x%2B15\"\r
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\n" ); document.write( "\n" ); document.write( " So this is the graph of \"y=-x%2B15\" through the points and \r
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\n" ); document.write( "\n" ); document.write( "Now let's graph the second equation:\r
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\n" ); document.write( "\n" ); document.write( "\"x-y=3\" Start with the second equation.\r
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\n" ); document.write( "\n" ); document.write( "\"-y=3-x\" Subtract \"x\" from both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"y=%283-x%29%2F%28-1%29\" Divide both sides by \"-1\" to isolate \"y\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=x-3\" Rearrange the terms and simplify.\r
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\n" ); document.write( "\n" ); document.write( "Looking at \"y=x-3\" we can see that the equation is in slope-intercept form \"y=mx%2Bb\" where the slope is \"m=1\" and the y-intercept is \"b=-3\" \r
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\n" ); document.write( "\n" ); document.write( "Since \"b=-3\" this tells us that the y-intercept is .Remember the y-intercept is the point where the graph intersects with the y-axis\r
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\n" ); document.write( "\n" ); document.write( "So we have one point \r
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\n" ); document.write( "\n" ); document.write( "Now since the slope is comprised of the \"rise\" over the \"run\" this means\r
\n" ); document.write( "\n" ); document.write( "\"slope=rise%2Frun\"\r
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\n" ); document.write( "\n" ); document.write( "Also, because the slope is \"1\", this means:\r
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\n" ); document.write( "\n" ); document.write( "\"rise%2Frun=1%2F1\"\r
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\n" ); document.write( "\n" ); document.write( "which shows us that the rise is 1 and the run is 1. This means that to go from point to point, we can go up 1 and over 1\r
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\n" ); document.write( "\n" ); document.write( "So starting at , go up 1 unit \r
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\n" ); document.write( "\n" ); document.write( "and to the right 1 unit to get to the next point \r
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\n" ); document.write( "\n" ); document.write( "Now draw a line through these points to graph \"y=x-3\"\r
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\n" ); document.write( "\n" ); document.write( " So this is the graph of \"y=x-3\" through the points and \r
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\n" ); document.write( "\n" ); document.write( "Now let's graph the two equations together:\r
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\n" ); document.write( "\n" ); document.write( " Graph of \"y=-x%2B15\" (red). Graph of \"y=x-3\" (green)\r
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\n" ); document.write( "\n" ); document.write( "From the graph, we can see that the two lines intersect at the point . So the solution to the system of equations is . This tells us that the system of equations is consistent and independent.\r
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