A cura di: Alfredo Bochicchio

$2ab-(1/3a^2b-1/9a^2b)+(3/2ab-2ab)+(-2/9a^2b+a^2b)-1/2ab+(-5/9a^2b)$
$2ab-(3-1)/9a^2b+(-1/2ab)+(-2+9)/9a^2b-1/2ab-5/9a^2b$
$2ab-2/9a^2b+(-1/2ab)+(-2+9)/9a^2b-1/2ab-5/9a^2b$
$2ab-2/9a^2b-1/2ab+7/9a^2b-1/2ab-5/9a^2b$
$2ab-1/2ab-1/2ab-2/9a^2b+7/9a^2b-5/9a^2b$
$(2-1/2-1/2)ab+(-2/9+7/9-5/9)a^2b$
$(4-2)/2ab+5/9-5/9a^2b$
$2/2ab$
$ab$