Espressioni con i prodotti notevoli

$$\left( a+2b\right) ^{2}+\left( a+b\right) \left( a-b\right) +4a\left( 1-a\right) =$$

$$a^{2}+4ab+4b^{2}+a^{2}-b^{2}+4a-4a^{2}=$$

$$-2a^{2}+4ab+3b^{2}+4a$$

Ordino i monomi in base al grado:

$$-2a^{2}+3b^{2}+4ab+4a$$

$$\left( 2a+3b\right) \left( 2a-3b\right) -\left( 2a-3b\right) ^{2}+3b\left( 3-4a\right)=$$

$$4a^{2}-9b^{2}-4a^{2}+12ab-9b^{2}+9b-12ab=$$

$$ -18b^{2}+9b$$