Question

Выполните действия:
1) 9/a - 18/a²+2a
2) 3x-15/x+4 ÷ x²-25/3x+12

Answer 1

$1) \frac{9}{a} - \frac{18}{a^2+2a} = \frac{9}{a} - \frac{18}{a(a+2)} = \frac{9(a+2)-18}{a(a+2)} = \frac{9a+18-18}{a(a+2)} = \frac{9a}{a(a+2)} = \frac{9}{a+2} \\ \\ 2) \frac{3x-15}{x+4} : \frac{x^2-25}{3x+12} = \frac{3(x-5)}{x+4} : \frac{x^2-5^2}{3(x+4)} = \frac{3(x-5)}{x+4} * \frac{3(x+4)}{(x-5)(x+5)} = \\ \\ = \frac{3*3*(x+4)(x-5)}{(x+5)* (x+4)(x-5)} = \frac{9}{x+5}$