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Coordinate Geo

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Coordinate Geo

by yellowho » Sat Feb 26, 2011 2:14 am
Anybody have a good system for solving coordinate geometry that involves y-intercept, x-intercept, slopes. Basically problems that gives you one or two of these info. for two lines and you have to find others. These are not hard and so time consuming and easy to make a mistake like forgetting a case/scenario.

I've actually sat down and try various combinations. Doesn't appear there are any useful patterns. What is the best approach to attack these problems?
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by Tani » Tue Mar 01, 2011 2:16 pm
You have to go back to y= mx +b

If you have slope (m) and y intercept (b) simply plug them in.

If you have slope (m) and x intercept, plug in m and set y = 0

If you have both intercepts, you have two points and can use the formula for the slope (y2 - y1)/(x2-x1) to get m
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by tm4733 » Thu Mar 03, 2011 9:31 am
The MGMAT Geometry book does a decent job of laying out the different cases. Also, refer to a basic SAT book. Here are the two systems I use

(1) y=mx+b
(2) y-y1=m(x-x1) [(x1,y1) are points; m is the slope; x,y are variables in the equation]
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