Question

срочнооо даю 90балоовввввввввввввввв​

Answer 1

Ответ:

Применяем формулы:  $\bf a^2-b^2=(a-b)(a+b)\ \ ,$  

                                         $\bf a^2-2ab+b^2=(a-b)^2$   .

$\displaystyle 1)\ \ \frac{y^2-9}{27y^2}\cdot \frac{9y}{y-3}=\frac{(y-3)(y+3)}{3y}\cdot \frac{1}{y-3}=\frac{y+3}{3y}\\\\\\2)\ \ \frac{x^2-49}{3x^3}\cdot \Big(-\frac{x}{7-x}\Big)=\frac{-(x-7)(x+7)}{3x^2}\cdot \frac{x}{7-x}=\frac{x+7}{3x}\\\\\\3)\ \ -\frac{x^2-12x+36}{x^2-1}\cdot \frac{5x+5}{2x-12}=\frac{-(x-6)^2}{(x-1)(x+1)}\cdot \frac{5\cdot (x+1)}{2\cdot (x-6)}=\frac{-(x-6)\cdot 5}{2\cdot (x-1)}=\\\\=\frac{5\cdot (6-x)}{2\cdot (x-1)}$

$4)\ \ -\dfrac{m^2-6m+9}{n^2-4}\cdot \dfrac{2n-4}{3m-9}=\dfrac{-(m-3)^2}{(n-2)(n+2)}\cdot \dfrac{2(n-2)}{3(m-3)}=\dfrac{-(m-3)\cdot 2}{(n+2)\cdot 3}=\\\\=\dfrac{2\, (3-m)}{3\, (n+2)}$