Question

решите
${9x}^{2} - 360x - 9 = 0$

Answer 1

${9x}^{2} - 360x - 9 = 0 : 9 \\ {x}^{2} - 40x - 1 = 0 \\ D= b^{2} - 4ac = -40^{2} - 4*1**-1= 1600+4=1604= \sqrt{1604} \\ = 2\sqrt{401} \\ x_{1} = \frac{40-2\sqrt{401}}{2} = 20- \sqrt{401} \\ x_{2} = \frac{40+2\sqrt{401}}{2} = 20+\sqrt{401}$