Question

Решите уравнение (7-х) (9-х) =0

Answer 1

Ответ:

$(7 - x)(9 - x) = 0$

$7 \times 9 - 7x - 9x - x( - x) = 0$

$63 - 7x - 9x + {x}^{2} = 0$

$63 - 16x + {x}^{2} = 0$

${x}^{2} - 16x + 63 = 0$

$1 {x}^{2} - 16x + 63= 0$

$1 {x}^{2} + ( - 16x) + 63 = 0$

$a = 1.b = - 16.c = 63$

$x = \frac{ - ( - 16)± \sqrt{ {( - 16)}^{2} - 4 \times 1 \times 63} }{2 \times 1}$

$x = \frac{16± \sqrt{256 - 252} }{2}$

$x = \frac{16± \sqrt{4} }{2}$

$x = \frac{16± \sqrt[2]{ {2}^{2} } }{2}$

$x = \frac{16±2}{2}$

$x = \frac{16 + 2}{2} \\ x = \frac{16 - 2}{2}$

$x = \frac{18}{2} \\ x = \frac{14}{2}$

$x = 18 \div 2 \\ x = 14 \div 2$

$x = 9 \\ x = 7$

$x_{1} = 7. x_{2} = 9$