document.write( "Question 623042: The Compass practice test question is 'What is the equation of the line that contains the points with (x,y) coordinates (-3,7) and (5,-1')? I know the answer is y=x+4 but how do you go about getting that answer? Is there an easy formula to figure it out? Please show me step by step... \n" ); document.write( "

Algebra.Com's Answer #391798 by Earlsdon(6294) $\"\"$ $\"About$

You can put this solution on YOUR website!
Formula? No, I don't think so!
\n" ); document.write( "Here's one way to get the answer.
\n" ); document.write( "Start with:
\n" ); document.write( "y = mx+b Find the slope, m:
\n" ); document.write( " $\"m+=+%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29\"$ The x's and y's are the coordinates of the two given points, so we substitute:
\n" ); document.write( " $\"m+=+%28-1-7%29%2F%285-%28-3%29%29\"$ Evaluate.
\n" ); document.write( " $\"m+=+%28-8%29%2F8\"$
\n" ); document.write( " $\"m+=+-1\"$ so now you have:
\n" ); document.write( "y = -x+b To find b, substitute the x- and y-coordinates of either of the two given points. Let's choose (-3, 7) and substitute:
\n" ); document.write( "7 = -1(-3)+b Solve for b.
\n" ); document.write( "7 = 3+b Subtract 3 from both sides.
\n" ); document.write( "b = 4
\n" ); document.write( "The final equation is:
\n" ); document.write( "y = -x+4
\n" ); document.write( "Your answer is almost correct but you'll find that the slope, m, is negative! \n" ); document.write( "

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