Розділ 1. ЦІЛІ ВИРАЗИ » 361

Спрости вираз. a) (a + 1)(a – 3) + 2a(1 – a) = a2 – 3a + a – 3 + 2a – 2a2 = –a2 – 3; б) (3a + b)(a – b) – (3a2 – b2) = 3a2 – 3ab + ab – b2 – 3a2 + b2 = –2ab в) (3x + 1)(x – 6) + (2 – 3x)(x – 5) = 3x2 – 18x + x – 6 + 2x – 10 – 3x2 + 15x = –16; г) (x – y)(x + 7) – (y + x)(x + 7) + 14y = x2 + 7x – xy – 7x – (xy + 7y + x2 + 7x) + 14y = x2 + 7x – xy = 7y – xy – 7y – x2 – 7x + 14y = –2xy.