= 7(х² - 2xy + y²) - c(25a² + 10ac + c²) + a² + (16a² - 8ab + b²) - 9p² - (q² - 6pq + 9p²) + 9x² - (y² - 10xy + 25x²)= 7x² - 14xy + 7y² - 25ac - 10c² + a² + 16a² - 8ab + b² - 9p² - q² + 6pq - 9p² + 9x² - y² + 10xy - 25x²= 7x² - 14xy + 7y² - 25ac - 10c² + a² + 16a² - 8ab + b² - 9p² - q² + 6pq - 9p² + 9x² - y² + 10xy - 25x²
= 7(х² - 2xy + y²) - c(25a² + 10ac + c²) + a² + (16a² - 8ab + b²) - 9p² - (q² - 6pq + 9p²) + 9x² - (y² - 10xy + 25x²)
= 7x² - 14xy + 7y² - 25ac - 10c² + a² + 16a² - 8ab + b² - 9p² - q² + 6pq - 9p² + 9x² - y² + 10xy - 25x²
= 7x² - 14xy + 7y² - 25ac - 10c² + a² + 16a² - 8ab + b² - 9p² - q² + 6pq - 9p² + 9x² - y² + 10xy - 25x²