| (1) | $$ \begin{align} (x+2)(x+3) &= x^2+(2+3)x+2\times 3 \\ &= x^2+5x+6 \end{align}$$ |
| (2) | $$ \begin{align} (x-6)(x-4) &= x^2+(-6-4)x+(-6)\times (-4) \\ &= x^2-10x+24 \end{align}$$ |
| (3) | $$ \begin{align} (x+9)(x-5) &= x^2+4x-45 \end{align}$$ |
| (4) | $$ \begin{align} (x+5)(x-8) &= x^2-3x-40 \end{align}$$ |
| (5) | $$ \begin{align} (a-1)(a+2) &= a^2+a-2 \end{align}$$ |
| (6) | $$ \begin{align} (y+2)(y-6) &= y^2-4y-12 \end{align}$$ |