x(x + 8) < 0
-∞__+__( -8 )_-_( 0 )__+__+∞
x ∈ (-8; 0)
x(x + 7) > 0
-∞__+__( -7 )_-_( 0 )__+__+∞
x ∈ (-∞; -7) U (0; +∞)