It is known that the odd function f (x) defined on R satisfies f (x + 4) = - f (x) and is an increasing function in the interval [0,2]. If the equation f (x) = m (M > 0) has four different roots x1, X2, X3, X4 in the interval [- 8,8], then what is X1 + x2 + X3 + X4 equal to

It is known that the odd function f (x) defined on R satisfies f (x + 4) = - f (x) and is an increasing function in the interval [0,2]. If the equation f (x) = m (M > 0) has four different roots x1, X2, X3, X4 in the interval [- 8,8], then what is X1 + x2 + X3 + X4 equal to

F (x) satisfies that f (x + 4) = - f (x), f (x + 8) = f [(x + 4) + 4] = - f (x + 4) = f (x), then f (x) is a periodic function, and the period T = 8. F (x) is an odd function, and it is an increasing function on [0,2], then it is also an increasing function on [- 2,0], and f (0) = 0, then f (x) is continuous, and it is an increasing function on [- 2,2]. According to f (x + 4) = - f (x), the image of F (x) on [2,6] is a decreasing function, 8] Draw a diagram: get X1 + x2 = - 12, X3 + X4 = 4, so X1 + x2 + X3 + X4 = - 8