Умножить
1)(c+3)(c+9)
2)(y-8)(y+7)
3)(2a-1)(3a+4)
4)(5x-2y)2 (во второй степени)
5)3a(a-b)-(a+b)(3a-b)

1) (c+3)*(c+9) = c² + 9c + 3c + 27 = c² + 12c + 27

2) (y-8)*(y+7) = y² + 7y - 8y - 56 = y² - y - 56

3) (2a-1)*(3a+4) = 6a² + 8a - 3a - 4 = 6a² + 5a - 4

4) (5x-2y)*2² = (5x-2y)*4 = 20x - 8y

5) 3a*(a-b)-(a+b)*(3a-b) = 3a² - 3ab - (3a² - ab + 3ab - b²) = 3a² - 3ab - (3a² + 2ab - b²) = 3a² - 3ab - 3a² - 2ab + b² = -5ab + b²