(x+1)(x+2)>0

plot -1 , -2 on the number line. since the expression is greater than zero hence the answer will be x belongs to (-infinity,-2)union(-1,+infinity).

it is so simple

find their exreme point

which are -1 and -2 are respectively now draw a no line locate these point on that line

then point divide that line in three part  take the positive side on the no. line as equation is gr. than 0

so domain is 

(-∞,-2)U(-1,∞)

X<-2 or X>-1