(7a +2b)² - (3a -b)(4a - 55) =
= (7a)² + 2*7a*2b + (2b)² - (3a*4a + 3a *(-55) - b *4a -b *(-55)) =
= 49a² + 28ab + 4b² - (12a² - 165a - 4ab +55b) =
= 49a² + 28ab +4b² - 12a² + 165a + 4ab - 55b =
= (49a² - 12a²) + (28ab + 4ab) + 165a + 4b² - 55b =
= 37a² + 32ab + 165a + 4b² - 55b