I am a bit confused. http://pokit.org/get/bedc0ac7e1d17e01d7d58b021b81663c.jpg [Broken] The function is y=x(2t) and the point of it is to show the property of time-invariance.(which we should fail in this example, because it isn't time invariant.) Input signal is x1(t) Output signal is shown for that signal y1(t) But when you shift it, x1(t-2) it doesn't give y1(t-2). I am both ok and not ok with that. First lets go over the math. If I shift my signal x1(t) by -2 I get [itex] y_2(t)=x(2(t-2)) [/itex] Is that correct? But that is [itex] y_2(t)=x(2(t-2))=x(2t-4) [/itex] and that is original signal, shifted by 4, and then scaled by 2, which is not what it should be. y2(0)=x(-4) which is 0, not 1. I am probably stuck on something simple, but nevertheless I am stuck.