Why is 'b' Used in Slope-Intercept Form?Date: 02/04/2004 at 19:43:02 From: Lucas Subject: Why is the letter "b" used for the y intercept in equations? My class has to find out the origin of the letter "b" used for the y-intercept in equations. For example, did it come from a word in another language having something to do with the y-intercept? Date: 02/04/2004 at 21:35:11 From: Doctor Rob Subject: Re: Why is the letter "b" used for the y intercept in equations? Thanks for writing to Ask Dr. Math, Lucas! The likely reason for using b for the y-intercept comes from a seldom seen form for the equation of a line. It applies only to lines neither vertical, nor horizontal, nor passing through the origin. It is called the two-intercept form: x/a + y/b = 1. Then the x-intercept is a and the y-intercept is b. Probably a and b are used because they are the first two letters of the alphabet. Solving for y, you can convert this form to slope-intercept form, and you get y = (-b/a)*x + b, so the slope is m = -b/a, and the y-intercept is b. Feel free to write again if I can help further. - Doctor Rob, The Math Forum http://mathforum.org/dr.math/ |
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