#-4#: #-4#, #color(green)(-2)#, #color(green)(-1)#, #color(green)1#, #color(green)2#, #4#
#2#: #color(green)(-2)#, #color(green)(-1)#, #color(green)1#, #color(green)2#
#color(green)(-2)#, #color(green)(-1)#, #color(green)1#, and #color(green)2# all work, so take into account the least common factor. That leaves you with #-2# because it is the smallest.