Question

Помогите пожалуйста!!

Answer 1

3.

$\dfrac{6ab^2}{21bc}\div\dfrac{3b}{3b}=\dfrac{2ab}{7c}$

Б

4.

$\dfrac{ab-5b}{10b}\div\dfrac{b}{b}=\dfrac{\frac{ab-5b}{b}}{\frac{10b}{b}}=\dfrac{a-5}{10}$

Г

5.

$\dfrac{x^2-4x+4}{x^2-4}=\dfrac{(x-2)^2}{(x+2)(x-2)}\div\dfrac{x-2}{x-2}=\dfrac{x-2}{x+2}$

6.

$\dfrac{4x}{x^2-25}+\dfrac{3}{x}=\dfrac{4x}{x^2-25}\times\dfrac{x}{x}+\dfrac{3}{x}\times\dfrac{x^2-25}{x^2-25}=\dfrac{4x^2}{x^3-25x}+\dfrac{3x^2-75}{x^3-25x}=\dfrac{7x^2-75}{x^3-25x}$

7.

$\dfrac{x-3}{3x}\times\dfrac{x}{x}+\dfrac{x-4}{x^2}\times\dfrac{3}{3}=\dfrac{x^2-3x}{3x^2}+\dfrac{3x-12}{3x^2}=\dfrac{x^2-4x+4x-12}{3x^2}=\dfrac{x^2-12}{3x^2}$

8.

$\dfrac{x+1}{2x+4}\times\dfrac{2-x}{2-x}-\dfrac{2}{4-x^2}\times\dfrac{2}{2}-\dfrac{x-1}{2x-4}\times\dfrac{-2-x}{-2-x}=\dfrac{(-x^2+x+2)-4-(-x^2-4x-2)}{8-2x^2}=\\\dfrac{-x^2+x+2-4+x^2+4x+2}{8-2x^2}=\dfrac{5x}{8-2x^2}$

9.

1)

$\dfrac{a+3b}{b}=2\implies \dfrac{a}{b}+3=2\implies\dfrac{a}{b}=-1$

2)

$\dfrac{a}b=-1\implies a=-b\implies b=-a\\\\\dfrac{5a+3b}{a}=\dfrac{5a-3a}{a}=\dfrac{2a}{a}=2$