document.write( "Question 215544: Write a rule for the graph with X = 1, 2, 3, 4 and y = 2, 8, 14, 20. x being the domain and y the range \n" ); document.write( "
Algebra.Com's Answer #162866 by Edwin McCravy(20056)\"\" \"About 
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Write a rule for the graph with X = 1, 2, 3, 4 and y = 2, 8, 14, 20. x being the domain and y the range
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document.write( "We plot the points (1,2), (2,8), (3,14), (4,20).\r\n" );
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document.write( "We notice that we can draw a straight line through them, like this:\r\n" );
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document.write( "So we find the equation of the line that passes through two of them,\r\n" );
document.write( "say the first two, (1,2) and (2,8)\r\n" );
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document.write( "find the slope, using the formula:\r\n" );
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document.write( "\"m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29=%288-2%29%2F%282-1%29=6%2F1=6\"\r\n" );
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document.write( "Then substitute in the point-slope equation:\r\n" );
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document.write( "\"y-y%5B1%5D=m%28x-x%5B1%5D%29\"\r\n" );
document.write( "\"y-2=6%28x-1%29\"\r\n" );
document.write( "\"y-2=6x-6\"\r\n" );
document.write( "\"y=6x-4\"\r\n" );
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document.write( "Now we check to see if (3,14) and (4,20) satisfy the\r\n" );
document.write( "equation:\r\n" );
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document.write( "Substituting (3,14),\r\n" );
document.write( "\"y=6x-4\"\r\n" );
document.write( "\"14=6%283%29-4\"\r\n" );
document.write( "\"14=18-4\"\r\n" );
document.write( "\"14=14\" \r\n" );
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document.write( "So (3,14) satisfies it and is therefore on the line.\r\n" );
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document.write( "Substituting (4,20),\r\n" );
document.write( "\"y=6x-4\"\r\n" );
document.write( "\"20=6%284%29-4\"\r\n" );
document.write( "\"20=24-4\"\r\n" );
document.write( "\"20=20\" \r\n" );
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document.write( "So (4,20) satisfies it also and is therefore on the line.\r\n" );
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document.write( "Therefore thew correct equation is\r\n" );
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document.write( "\"y=6x-4\"\r\n" );
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document.write( "Edwin
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