Further Maths Matrices HELP

Here s the question:


( s is a 2x2 matrix)
S = ( -0.28 0.96 )
( 0.96 0.28 )
Show that the invariant points of matrix s lie on a straight line, and find the equation of this line.

I tried to solve it by placing it through a x, y matrix but I get two equations which arent equivalent .

0 = 0.96y - 1.28x
0 = 1.28y - 0.96x

What should I be doing instead?