Factories:

36c2 – (5a + b)2

Given,


36c2 – (5a + b)2


= (6c)2 – (5a + b)2


By using the formula a2 – b2 = (a + b)(a – b)


We get,


36c2 – (5a + b)2 = (6c)2 – (5a + b)2


= {(6c) + (5a + b)}{(6c) – (5a + b)}


= (6c + 5a + b)(6c – 5a – b)


20