First of all, I think the equation should be CFO=NI-/+gain/loss from financing or investment cash flows+NCCs- chg of working  capitals. In the second, in my opinion, this equation is just one for you to calculate the CFO from B/S and I/S, not a definition of CFO. CFO is cash flow from operations, as the Notes presents, depreciation is noncash expense aside from any taxes so it doesn't have any cash flows. From this aspect. depreciation cannot affect the cash flows from operating. And I think this can explain your second question about impairment as well, just like depreciation, impariment is also a noncash item, so it cannot affect cash flows such as CFO.

thz for ur replying:D understood!