Bài giải:
a. $(-1005).(x+2)=0$
<=>$-1005x-2010=0$
<=>$ x =2010:(-1005)$
<=>$ x =-2$
b. $(8+x).(6-x)=0$
<=>$\left \{ {{8+x=0} \atop {6-x=0}} \right.$
<=>$\left \{ {{x=-8} \atop {x=6}} \right.$
c. $8x.(5-x)=0$
<=>$\left \{ {{8x=0} \atop {5-x=0}} \right.$
<=>$\left \{ {{x=0} \atop {x=5}} \right.$
d. $x^2-5x=0$
<=>$x.(x-5)=0$
<=>$\left \{ {{x=0} \atop {x-5=0}} \right.$
<=>$\left \{ {{x=0} \atop {x=5}} \right.$