Devi ridurre i monomi simili liberando le parentesi.
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$(-6x^2+14a-3)-(7x^2+11a+2)-(-2x^2+9a+1)$
$-6x^2+14a-3 -7x^2-11a-2 +2x^2-9a-1$
$(-6-7+2)x^2+(14-11-9)a +(-3-2-1)$
$-11x^2+(-6)a +(-6)$
$-11x^2-6a -6$
x^2(-6-7+2)+a(14-11-9)-6
-11x^2-6a-6
-(11x^2+6(a+1))