Desarrolla $\left(0$ left $\left(-2x-3y$ \ $1gnt\right)$ $21\right)\left(-2x-3y^{2}\right)$

$\dfrac {\left(x+12\right)1\left(x-6\right)1-\left(x+10\right)1\left(x-4\right)} {\left(x-6\right)1\left(x+10\right)1}$

1) ) $\left(x+2\right)\left(x+3\right)=$ 2) $\left(x-2\right)\left(x-3\right)=$ 3) $\left(x+2\right)\left(x-3\right)$ = 4) $\left(x-2\right)\left(\times +3\right)$ %3D 5) $\left(\times +9\right)\left(x+4\right)$ = 6) $x-8\right)\left(x-6\right)=$ = 7) $\left(x+12\right)\left(x-8\right)=$ 8) $\left(x-3\right)\left(x-4\right)=$ 9) $\left(2x+1\right)\left(2x+5\right)$ 10) $\left(2x-3\right)\left(2\times +7\right)$ 1) $\left(3x+6\right)\left(3x-9\right)=$ 12) $\left(5\times +3\right)\left(5x-8\right)=$ $13\right)$ $\left(x-1\right)\left(x+4\right)=$ 74) $\left(a+15\right)\left(a-9\right)=$ $15\right)$ $\left(a^{2}+3\right)\left(a^{2}-5\right)=$ $\left(a^{2}+4\right)\left(a^{2}+2\right)=$ $|6\right)$