TI83 - Two lines intersecting

[Acidic]

Does anyone have a TI83 and know how to write a program for it where it tells you if and where two (2-D) lines intersect (actually 3-D would be nice too). I probably could do this myself given time but I'm sure someone out there can do it better.

I figured this would be the most appropriate forum for this.

[jemidiah]

You could go the very complicated way and subtract the equations programatically, or you could go the simple route and subtract the two equations after being evaluated for many values of x (only in one direction, ie. when the absolute value of their difference gets smaller) and wait until the difference becomes an arbitrary epsilon (it would probably not actually reach zero unless your x step was infinitely small) which is very close to zero. I could probably write a progam for it later if needed.

[Acidic]

not needed, I only thought it might be fun to have. For the moment I can always write the two eqns into the graph thingy and use the inbuilt function to find their intersection.

[sql_lall]

so you just want the intersection of two line....no problems.
How do you have the lines...y=mx + c???

you see, if you have them of the form "Ax + By = C" then it is really easy, using the Ti83 matrix stuff:
Ax + By = C
Dx + Ey = F
Let matrix J = [[A,B][D,E]]^-1
=> [[x, y]] = J [[C, F]]

All you would have to do is check that
A/D != B/E
cos that means that the lines are parallel. In that case:
A/B=B/E=C/F means they are the same line
A/B=B/E <> C/F means they never intersect

[Acidic]

'nuff said