FCFF question

So I passed level 1, but have always struggled with the multiple formulas that can be used to calculate this, particularly when net capital investment and working capital investment is involved. I need to wrap my head around this as this is pretty basic. I’m hoping maybe a clear explanation from someone will shore up what I’m missing here. From Schweser:

FCFF = NI + non-cash charges + [interest expense x (1-tax rate)] - net capital investment - working capital investment


FCFF = CFO + [interest expense x (1-tax rate)] - net capital expenditure

I’m thinking my struggle here is the difference between investment vs expenditure. Clearly, CFO =/= NI + non-cash charges only. The indirect method is much more involved in looking at changes in the balance sheet items. Should I be interpreting “working capital investment” as all of those missing pieces? As in : (- positive changes in AR and Inv or + (minus minus) negative changes in AR and Inv) ? What about the changes in the liabilities?

What about net capital investment vs. net capital expenditure?

Any help would be appreciated here…

Net capital investment = capex, I believe

Working cap is changes in A/R & Inv & A/P etc…

giving an example w/ #s may help…