[Risolto] help

(x + 2·y)·(x - 2·y) - 3·x·(x - 1) + (2·x - 1)^2 + (- 2·y)^2=

=(x^2 - 4·y^2) - (3·x^2 - 3·x) + (4·x^2 - 4·x + 1) + 4·y^2=

=2·x^2 - x + 1