Does anyone know how to do simultaneous equations on a TI-89? For instance if I had something like "2x+3y=5 and 4x+5y=2" how would I plug that into the calculator?

solve(2x+3y=5 and 4x+5y=2,{x,y})

OK, thanks. I was using regular paranthesis instead of brackets.

That, or set the equations up in a matrix and use the rref() function to let it do the work.

i.e. for 2x + 3y = 5 and 4x + 5y = 2 you should set up the following matrix:

[[2,3,5]
[4,5,2]]

making sure that you keep your variables in consistent alignment throughout (i.e. all the x coefficients in one column, etc.) Hit Enter to let the calculator accept the matrix (or save it to a named matrix), and then hit rref(ans). The calculator should return:

[[1,0,x-value]
[0,1,y-value]]

You can set up and solve a N-by-(N+1) matrix for any system of N simultaneous equations. And this will work on any TI graphical calculator, as well as any calculator with the rref function. In the case of bigger matrices, the 1 will tell you which variable is being solved on that line.