(a-√5)(2a+2b)=2a2+2ab+2√5a+2√5b
(a-√5)(2a+2b) = 2a² + 2ab - 2a√5 - 2b√5
(a-√5)(2a+2b)=2a^2 + 2ab- 2a√5 - 2b√5