Question

Помогите пожалуйста

Answer 1

Ответ:

${x}^{2} - 9x + 20 = 0 \\ d = {b }^{2} - 4ac = 81 - 4 \times 20 = 4 \\ x = b - \sqrt[2]{d} \div 2a \\ x = 9 - 1 \div 2 = \frac{8}{2 } = + - 4$