Quadratic Equation And Inequalities

Let \(\alpha_1,\alpha_2,....,\alpha_7\) be the roots of the equation \({x^7} + 3{x^5} - 13{x^3} - 15x = 0\) and \(|{\alpha _1}| \ge |{\alpha _2}| \ge \,...\, \ge \,|{\alpha _7}|\). Then \(\alpha_1\alpha_2-\alpha_3\alpha_4+\alpha_5\alpha_6\) is equal to _________.