Special Relativity and reference frames

[authenticgeek]

Here's a statement that I'm supposed to solve:

($$\Delta$$x')² = ($$\Delta$$x)² - c²($$\Delta$$t)²

And the accompanying text: "Show that (the equation above) is the same for all reference frames in special relativity"

I consider myself somewhat decent with your basic special relativity calculations but I'm having trouble starting this one. I'm not interested in an answer as much as a gentle nudge in the correct direction.

What is this question asking for, mathematically? I don't even know where I should be ending up...

 

[Dick]

It's asking you to assume (x',t') and (x,t) are related by a Lorentz transformation and show that (delta t')^2*c^2-(delta x')^2=(delta t)^2*c^2-(delta x)^2.