Формула разности квадратов :

[tex]\displaystyle\bf\\\Big(a-b\Big)\cdot\Big(a+b\Big)=a^{2} -b^{2} \\\\\\\Big(12c-411d\Big)\cdot\Big(12c+411d\Big)=\Big(12c\Big)^{2} -\Big(411d\Big)^{2} =\\\\\\=144c^{2} -168921 d^{2}[/tex]