If f (x) is differentiable on R and has two real roots, it is proved that its derivative has at least one real root; if f (x) has three real roots, it is proved that its second derivative has better one real root Urgent request

F (x) is differentiable and has two real roots, that is, there are two points such that f (x1) = f (x2) = 0,
According to the mean value theorem, in the interval [x1, X2], there must be a point x such that f '(x) * (x2-x1) = f (x2) - f (x1) = 0;
Since x1 ≠ X2, there should be f '(x) = 0, that is, the function f' (x) has at least one zero point (a real root) in the interval;
Similarly, if there is x1

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