Date: 08/15/97 at 05:06:34 From: Elizabeth Subject: Name of a graphing equation I need to find out how to graph the following equations. I know the coordinates but would like to know the name and where I can graph them. They are as follows: 4x-2y = 5 x = 3y-1 and: y = 2x+7 y = -x-3 Your help would be greatly appreciated! Elizabeth
Date: 08/15/97 at 08:19:44 From: Doctor Jerry Subject: Re: Name of a graphing equation Hi Elizabeth, All of these are equations of a line. They all can be put into the form A*x+B*y = C. The last two equations have the form y=m*x+b. These are often called the point-slope form of a line. The number m is the slope of the line and b is the y-intercept. To graph any one of these equations, all you need is two points that satisfy them. Since a line is completely determined by two of its points, this is all you need. The equation 4x-2y = 5, for example, is an equation for a line that goes through the points (0,-5/2) and (5/4,0). To find these two points, I first let x = 0 in the equation: 4*0-2y = 5. This is the same as -2y = 5 or y = -5/2, so (0,-5/2) is a point on the line. Next, let y = 0 in the equation and solve for x. This gives (5/4,0). You can do the same with y=2x+7: (0,7) and (-7/2,0) are two points on the line. Or you can notice that the slope of the line is 2 and its y-intercept is 7. If you know about slope, you can plot the line with this information. -Doctor Jerry, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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