The second problem x2>X 1 needs to be solved first, and let f(X)= X- radical x to prove its simple increase.

Certificate xn < A requires the relationship between xn- 1 and xn, and then proves it by mathematical induction.

The third problem is the observation structure, the core of which is the difference term and the column term, and the middle is about to take the beginning and the end.

Xn = root number xn- 1, Xn 2 = Xn- 1. Use this formula to convert parentheses into Xn+2 (Xn+2-Xn+ 1).

Because xn is incremental, it is all expanded to xn+2.

x3(x3-x2)+x4(x4-x3)+...+xn+2(xn+2-xn+ 1)& lt； xn+2(xn+2-x2)

Function g(x)=x(x-x2), xn+2 >；; X2 & gtX2/2, so g(x) increases, and xn+2 approaches A infinitely.

Since c = 0, a = 1.

xn+2(xn+2-x2)& lt； A(a-x2)= 1- radical B.

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