Factor out the 4 in both equations 8a^2-20^2=(2^2 times a^2 times 2)-(2^2 times 5) therefor it is also equal to (2a)^2 times 2-(2^2 times 5) we can force it into a difference of 2 perfect squares which is a^2-b^2=(a-b)(a+b) (2a√2)^2-(2√5)^2=((2a√2)-(2√5))((2a√2)+(2√5))
