Factories:
20a2 – 45b2
We have,
= 5(4a2 – 9b2)
By using the formula a2 – b2 = (a + b)(a – b)
We get,
20a2 – 45b2 = 5(4a2 – 9b2)
= 5{(2a)2 – (3b)2}
= 5(2a + 3b)(2a – 3b)