HP INC (HPQ) financial position

Hello. Student here. 

Been assigned to analyze HP Inc. (HPQ)'s financial strengths and weaknesses. The problem I have is that, their D/E ratios r in in the minuses for the past 6 yrs. Their leverage ratio was -16.7x last yr (have been minus for the past 6 yrs as well.) So the company is obviously very levereged. But their stock prices grew by 105% over the past 5 years, instead of the leverage ratio being a red flag. So I wanna know whats the catch here. Is it bc their FCF grew alot of the years and that is outweighing the liabilities?

Also, what other ratios should i use to comprehensively analyse a company's financial strengths and weaknesses. Ty