\(\left(1+2x\right)\cdot\left(1-2x\right)-\left(x+2\right)\cdot\left(x-2\right)\)
\(=1^2-\left(2x\right)^2-\left(x^2-2^2\right)\)
\(=1-4x^2-x^2+4\)
\(=-5x^2+5\)
(1 + 2x)(1 - 2x) - (x + 2)(x - 2)
= 1 - 2x + 2x(1 - 2x) - [x(x - 2) + 2(x - 2)]
= 1 - 2x + 2x - 4x2 - [x2 - 2x + 2x - 4]
= 1 - 2x + 2x - 4x2 - x2 + 2x - 2x - 4
= -5x2 - 3