How do I solve these questions?

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3. Let f(h) be 0(h2) as h > 0 and let 901) be 0(h) as h > 0. Show that f(h)g(h) is 0(h3) as h > 0. Let p(x) be a polynomial on the real line with real coefficients. Suppose that p' (x) most m real roots. Show that p(x) has has at most m + 1 real roots