Once you know a matrix's eigenvalues, eigenvectors show you the exact directions that only get stretched or shrunk — never rotated — when the matrix acts on them.
1-A 2-A 3-A 4-A | 5 λv 6 λI 7 = x+y=0, eigenvector (1,−1) 8 = −x+y=0, eigenvector (1,1) 9 = y=0, eigenvector (1,0) | 10 = Yes, it's a scalar multiple (5 times)