а) (5a+7b)² - 7ab = 25a² + 70ab + 49b² - 7ab = 25a² + 63ab + 49b²
б) -6(2x-y)² = -6(4x² - 4xy + y²) = -24x² + 24xy - 6y²
в) (c+7) - (1-c)² = c + 7 - (1 - 2c + c²) = c + 7 - 1 + 2c - c² = 2c + 6 - c²
а) (5a+7b)² - 7ab = 25a² + 70ab + 49b² - 7ab = 25a² + 63ab + 49b²
б) -6(2x-y)² = -6(4x² - 4xy + y²) = -24x² + 24xy - 6y²
в) (c+7) - (1-c)² = c + 7 - (1 - 2c + c²) = c + 7 - 1 + 2c - c² = 2c + 6 - c²