Вправи: 257

257. Подайте у вигляді дробу вираз:

1) a^–2 + a^–3 = 1\aa2 + 1a3 = a+1a3;

2) mn^–4 + m^–4n = m\m4n4 + n\n4m4 = m5+ n5n4m4;

3) (c^–1 – d^–1)(c – d)^–2 = (1\dc – 1\cd) • 1(c-d)2 = d-ccd • 1(c-d)2 = –c-d•1cd(c-d)2 = –1cdc-d = 1cd(d-c);

4) (x^–2 + y^–2)(x² + y²)^–1 = (1x2 + 1y2) • 1x2+ y2 = x2+ y2x2y2 • 1x2+ y2 = 1x2y2.