Question

х во 2 степени плюс 7 равно 8х

Answer 1

$x^{2} +7=8x \\ x^{2} -8x+7=0 \\ a=1;b=-8;c=7 \\ D= b^{2} -4ac=64-4*7=64-28=36 \\ x_{1} = \frac{-b+ \sqrt{D} }{2a} = \frac{8+6}{2} = \frac{14}{2} =7 \\ x_{2} = \frac{-b- \sqrt{D} }{2a} = \frac{8-6}{2} = \frac{2}{2} =1$