Question

Упростите!

1. $( frac{x+3}{x^2-3x}+ frac{12}{9-x^2}) : frac{3}{3+x}$

2. $( frac{1}{d} -1) * frac{4d}{1-d^2}$

Answer 1

$( frac{x+3}{x^2-3x}+ frac{12}{9-x^2}) : frac{3}{3+x}= frac{(x+3)^2-12x}{x(x-3)(x+3)}: frac{3}{3+x}= frac{(x-3)^2(3+x)}{3x(x-3)(x+3)}= frac{x-3}{3x}$

$( frac{1}{d} -1) frac{4d}{1-d^2} = frac{1-d}{d} cdotfrac{4d}{1-d^2} = frac{4d(1-d)}{d(1-d)(1+d)}= frac{4}{1+d}$