I was learning about the Non-Arbitrage and the Fundamental Theorem of Asset Pricing and I came across one part of it (Introduction to Mathematical Finance By David C. Heath Glen Swindle) which say it should be easy to show but I couldn't show it no matter how much I tried. The problem is following if have Non-Arbitrage, how to show that closure of M(P) equals to M(P) I was learning about the Non-Arbitrage and the Fundamental Theorem of Asset Pricing and I came across one part of it (Introduction to Mathematical Finance By David C. Heath Glen Swindle) which say it should be easy to show but I couldn't show it no matter how much I tried. The problem is following if have Non-Arbitrage, how to show that closure of M(P) equals to M(P)