First simplify and then evaluate: (2a + 1) ^ 2 - (2a + 1) (2a-1), where a = change sign 5-1 / 2

First simplify and then evaluate: (2a + 1) ^ 2 - (2a + 1) (2a-1), where a = change sign 5-1 / 2

Because (2a = 1) ^ 2 = 4A ^ 2 + 4A + 1
(2a+1)(2a-1)=4a^2-1
So the original formula = 4A ^ 2 + 4A + 1 - (4a ^ 2-1) = 4A
Substituting a = radical 5-1 / 2, the value is 4 * radical 5-1 / 2