Ответ: \[x^{2} = 2x + 8\] \[x^{2} - 2x - 8 = 0\] \[D_{1} = 1 + 8 = 9\] \[x_{1} = 1 + 3 = 4;\] \[x_{2} = 1 - 3 = - 2.\]