Question

Answer 1

Bài 4:

a: \(\dfrac{x+4}{x+5}:\dfrac{x+5}{x+6}:\dfrac{x+6}{x+4}\)

\(=\dfrac{x+4}{x+5}\cdot\dfrac{x+6}{x+5}\cdot\dfrac{x+4}{x+6}\)

\(=\dfrac{\left(x+4\right)^2}{\left(x+5\right)^2}\)

b: \(\dfrac{x-7}{x+8}:\left(\dfrac{x-7}{x-9}:\dfrac{x+8}{x-9}\right)\)

\(=\dfrac{x-7}{x+8}:\left(\dfrac{x-7}{x-9}\cdot\dfrac{x-9}{x+8}\right)\)

\(=\dfrac{x-7}{x+8}:\dfrac{x-7}{x+8}=\dfrac{x-7}{x+8}\cdot\dfrac{x+8}{x-7}=1\)