Вправа 630 алгебра Бевз гдз 7 клас

№ 630

а) а² – b² – a – b = (a – b)(a + b) – (a + b) = (a + b)(a – b – 1);
в) 5a – 2c – 25a² + 4c² = 3(c – d) + (c – d)(c + d) =
= (c – d)(3 + c + d);
б) 3c – 3d + c² – d² = 4c² – 25a² + 5a – 2c =
= (2c – 5a)(2c + 5a) – (2c – 5a) = (2c – 5a)(2c + 5a – 1);
г) x² + у – у² + x = x² – y² + x + y = (x – y)(x + y) + (x + y) =
= (x + y)(x – y + 1);
ґ) x³ – a³ + x – a = (x – a)(x² + xa + a²) + (x – a) =
= (x – a)(x² + xa + a² + 1);
д) a + b – a³ – b³ = a + b – (a + b)(a² – ab + b²) =
= (a + b)(1 – a² + ab – b²).