1) (5b+6) (5b-6)

2) (5c+2a) (5c-2a)

3) (3x-y) (3x+y)

4) (4a-b) (b-4a)

1) (a + b) * (a - b) = a² - b²,

(5b + 6) * (5b - 6) = 5b² - 6² = 5b² - 6² = 5b² - 36 = 25b² - 36.

2) (a + b) * (a - b) = a² - b²,

(5c + 2a) * (5c - 2a) = 5c² - 2a² = 25c² - 4a².

3) (a + b) * (a - b) = a² - b²,

(3x - y) * (3x + y) = 3x² - y² = 9x² - y².

4) (a + b) * (a - b) = a² - b²,

(4a - b) * (b - 4a) = 4a² - b² = 16a² - b².