Question

Помогите пожалуйста

Answer 1

$(x - 9) \div \frac{ {x}^{2} + 18x + 81 }{x - 9} = (x + 9) \times \frac{x - 9}{ {(x + 9)}^{2} } = \frac{21 - 9}{21 + 9} = \frac{12}{30} = 0.4$