Need help with these ASAP not sure if the photo is turning up though will give brainliest and 30 points to the first correct answers

28) (a - 3b)(a + 2b)

29) 7(c - 2b)(c + 16b)

30) ½(a²)(a - 5)(a + 4)

Step-by-step explanation:

1) a² - ab - 6b²

a² - ab + (0.5b)² - 6.25b²

(a - 0.5b)² - (2.5b)²

(a - 0.5b - 2.5b)(a - 0.5b + 2.5b)

(a - 3b)(a + 2b)

7c² + 112bc - 252b²

7(c² + 16bc - 36b²)

7(c² + 16bc + (8b)² - 100b²)

7[(c + 8b)² - 100b²]

7[(c + 8b)²- (10b)²]

7[(c + 8b - 10b)(c + 8b + 10b)]

7(c - 2b)(c + 16b)

a⁴/2 - a³/2 - 10a²

(a²/2)(a² - a - 20)

(a²/2)[a² - a + (½)² - (½)² - 20]

(a²/2)[(a - ½)² - 81/4]

(a²/2)(a - ½ - 9/2)(a - ½ + 9/2)

½(a²)(a - 5)(a + 4)

i have no clue at all sorry

step-by-step explanation: