This is an equation and the idea is to find the value of #x# that makes the right side equal (equation) to the left one. To do that try to ISOLATE #x# on one side and send the numbers to the other side of the #=# sign. Remember that every time a term "crosses" the #=# sign it changes sign!
So: take #-1# and send it to the left (changing sign):
#-4+1=x#
evaluate #-4+1#
#-3=x#
So, finally, you got that the value of #x# that satisfies your equation is #-3#!
If you substitute #-3# in your equation in place of #x#, you'll get:
#-4=-1color(red)(-3)# which is true.
