978. 1) \(\frac{a^2-b^2}{a+b}\) ; 2) \(\frac{x^2-4x+4}{x^2-4}\) ; 3) \(\frac{a^3-b^3}{2a-2b}\) ; 4) \(\frac{1-x^3}{3+3x+3x^2}\)

Решение:

1. \(\frac{a^2-b^2}{a+b} = \frac{(a-b)(a+b)}{a+b} = a-b\)

2. \(\frac{x^2-4x+4}{x^2-4} = \frac{(x-2)^2}{(x-2)(x+2)} = \frac{x-2}{x+2}\)

3. \(\frac{a^3-b^3}{2a-2b} = \frac{(a-b)(a^2+ab+b^2)}{2(a-b)} = \frac{a^2+ab+b^2}{2}\)

4. \(\frac{1-x^3}{3+3x+3x^2} = \frac{(1-x)(1+x+x^2)}{3(1+x+x^2)} = \frac{1-x}{3}\)

Ответ: 1) \(a-b\); 2) \(\frac{x-2}{x+2}\); 3) \(\frac{a^2+ab+b^2}{2}\); 4) \(\frac{1-x}{3}\).