A cura di: Alfredo Bochicchio

$-3/2x^2y^4+(-4x^4y)+1/7x^2y^4-(-2x^4y)$
$-3/2x^2y^4-4x^4y+1/7x^2y^4+2x^4y$
$(-3/2+1/7)x^2y^4-4x^4y+2x^4y$
$(-21+2)/14x^2y^4-2x^4y$
$-(19/14)x^2y^4-2x^4y$