This document is written to show that computer algebra systems rref command should be used carefully when a matrix contains a parameter. Fortunately, for a square system, values of the parameter that may cause problems can be detected when we find the zeros of the determinant. This fits into a linear algebra course.
We point out the following remarks. When asked to compute the line of intersection of two planes, students usually proceed by finding the direction vector of this line with the cross product of the two normal vectors (one for each plane); eventually they find the parametric equations of the line. This is exactly what the solve or linsolve commands of TI-Nspire CAS yield!