Graphing InterceptsDate: 11/06/97 at 22:16:05 From: Scott J. Guenther Subject: Help on Algebra graph intercepts Hi. How would I find the intercept for a problem such as 3x-2y = 12? Any help would be appreciated. Thanks. Date: 11/10/97 at 11:18:44 From: Doctor Otavia Subject: Re: Help on Algebra graph intercepts Hello! When you speak of intercepts, it helps to know which one you're referring to. In the plane, unless a line is parallel to either the x-axis or the y-axis, it will intersect both axes sometime. We know this because two non-parallel lines in the same plane will intersect sometime. So then, since I'm not sure which intercept you want, I'll show you how to find both the x-intercept, or where the line intersects the x-axis, and the y-intercept, where the line interesects the y-axis. One really easy way to think about this is to try to visualize the problem. Where will a line intersect the x-axis? If you draw it, you'll see that it will always interesect the x-axis at a point where the y-coordinate is 0. This applies also to the y-intercept, but in reverse - a line will intersect the y-axis at a point where the x-coordinate is 0. So one way to solve this problem is to set x = 0 and solve for y, thus finding the y-intercept, and then set y = 0, solve for x, and find the x-intercept. Another way to do this is to put your line into slope-intercept form. That is when the equation for the line is in the form y = mx + b where m is the slope and b is the y-intercept. (Really, this is the same as the other way, because when x = 0, y = b.) Then the x- intercept is -b ----- m (which is the same as setting y = 0.) So you see, either way works. I hope this helps! -Doctor Otavia, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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