Elem Algebra / Discussion

This is the discussion related to the wiki page Elem Algebra.

forcing the axes to cross at (0,0)

Bruce Yoshiwara (guest) 22 Jun 2009 17:39

The query "y=5+3x" will result in two graphs, the first of which appears to show a line with negative vertical intercept.

The truth is that the vertical line marked with the vertical scale is not the y-axis, but x=-1.69.

The query "y=5+3x, x from 0 to 10" will result in a single graph that appears to show a line through the origin, but in this case the horizontal line marked with the horizontal scale is not the x-axis, but y=5.

Although I recognize that graphs often do not show the axes, I'd like a soft introduction for my developmental students.

How do we force W|Alpha to put the "AxesOrigin" at (0,0)?

changes regarding y=5+3x

Bruce Yoshiwara 31 Jul 2009 17:10

There has been at least 1 change since June 22 in Walpha outputs. By July 26, the query "y=5+3x" produced no graph at all rather than the two described in my previous post, and neither "graph y=5+3x" nor "plot y=5+3x" produced a graph. But as Gizem Karaali pointed out to me, "line y=5+3x" will produce a line and the axes do cross at (0,0).

Victoria Kim (guest) 20 Jul 2011 17:35

Thanks for following up and sharing the answer to your question.

Victoria Kim (guest) 20 Jul 2011 17:52

I think it is helpful for the students to put in numbers for the axes, especially if they are trying to match it to a graph they already have. For example, you can say plot y=3x+5 from -10 to 10, and it will show that part of the axes.