Question

7. Решите уравнение: ​

Answer 1

Х2-9|х|+20=0

Х2-9х+20=0 х>0
Х2-9*(-х)+20=0 х<0

Х=4, х=5; х>0
Х=-5, х=-4; х<0

Х=4, х=5
Х=-5, х=-4

Ответ: х1=4, х2=5, х3=-5, х4=-4

Answer 2

Ответ:

${x}^{2} - 9x = 20 \\ {x}^{2} - 9x = - 20 \\ d1 = 81 - 4 \times ( -20) = 161 \\ d2 = 81 - 4 \times 20 = 1 \\ x1 = \frac{9 + \sqrt{161} }{2} \\ x2 = \frac{9 - \sqrt{161} }{2} \\ x3 = \frac{9 - \sqrt{1} }{2} = 4 \\ x4 = \frac{9 + \sqrt{1} }{2} = 5$