7b · (2b + 3) - (b + 6) · (b - 5) =
= 14b² + 21b - (b² + b - 30) =
= 14b² + 21b - b² - b + 30 =
= 13 b² + 20b + 30
7b · (2b + 3) - (b + 6) · (b - 5) =
= 14b² + 21b - (b² + b - 30) =
= 14b² + 21b - b² - b + 30 =
= 13 b² + 20b + 30