a)[tex]-16x^{3} +86x^{2} -176x +105 = 86x^{2} +105 -16x^{2} -176x[/tex]
b) [tex]x = -3, x_{2} = \frac{-3-\sqrt{5} }{2} , x_{3} = \frac{-3+\sqrt{5} }{2} , x_{4} = 0[/tex]
