Given the equation x ^ 2-kx-2 = 0 about X, let the two equations be X1 and X2, and 2 (x1 + x2) > x1x2, find the value range of real number K

From the relationship between root and coefficient, we get X1 + x2 = k, x1x2 = - 2,
In 2 (x1 + x2) > x1x2,
2k>-2,
k>-1

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