I need to make optimal risky portfolio, minimum variance portfolio and efficient frontier using Markowitz . But i don't know whether to used close price data or adjusted data. If i'm using adjusted data, did i have include some additional formula for the dividend?
It depends on how your portfolio needs to be tracked, if it's end-of-day or snapshot driven portfolio, you could take the close price data from any of the exchange traded. Else, adjusted data intraday prices.
For minimum variance portfolio, i suppose you take the vertex [x0 + a, y0] coordinates from hyperbola of set of possible mean-variance patterns from your set of possible underlyings. Dividends could be adjusted with the stock price, if underlying is call option, you may need to adjust with risk neutral pricing or what ever strategy you are using to derive the underlying prices.