Revising for an exam here and looking at last years papers I can across this question -

I am unsure of what actually is 'f' in this case.

Is it (t^2 - 4) or do is f the integral of (t^2 - 4)?

And if it is the integral of (t^2 - 4) how am I supposed to integrate that when the values given are 0 and X. I have never seen an X in this location of the integration notation before so I'm not sure what to do with it?