1. (5x+7y) (2x – 3y) = 10x2 – xy + xy – 21y2 = = 10x2 – xy – 21y2.

Решим уравнение.

1. (5x + 7y) (2x – 3y) = 10x² - 15xy + 14xy – 21y² = 10x² – xy – 21y².

Заполним пропуски.

1. (5x + 7y) (2x – 3y) = 10x² – 15xy + 14xy – 21y² = = 10x² – xy – 21y².

Ответ: 15; 14.