Вправи: 361

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.