Hi Y'all! Is someone able to explain how to solve a modulus function like this example, |x-4|-|x+2|=6 . I understand that you can square both sides, but I'm not that confident with dealing with the modulus functions. Thanks in advance
The easiest way (I reckon, people will argue) is to split it up into sections. With two mod functions, you need to go bit by bit. So, we start with one of them:
|x-4|
=x-4 when x-4>=0 ---> x>=4
=-x+4 when x-4<0 ---> x<4
|x+2|
=x+2 when x+2>=0 ---> x>=-2
=-x-2 when x+2<0 ---> x<-2
Okay, so putting those together, we have 4 different scenarios:
1. x>=4 and x>=-2 (x-4 and x+2)
2. x<4 and x>=-2 (-x+4 and x+2)
3. x>=4 and x<-2 (x-4 and -x-2)
4. x<4 and x<-2 (-x+4 and -x-2)
Next, we need to reduce this into different segments where both of those conditions are true.
So, for 1, both situations are true whenever x>=4. For 2, both situations are true for -2<=x<4. For 3, there is no situation where both of those are true. And for 4, both of those are true if x<-2. So, putting that altogether, we have:
1. x-4-(x+2)=6, x>=4
2. -x+4-(x+2)=6, -2<=x<4
4. -x+4-(-x-2)=6, x<-2
Solving these, you'll get:
1. x-4-x-2=-6=6 (Nonsense, ignore this solution)
2. -x+4-x-2=-2x+2=6 ---> -2x=4 ---> x=-2 (this agrees with our bounds, keep it)
4. -x+4+x+2=(x-x)+6=6 (True for any x in this condition - that is, x<-2)
So, the solution is both x=-2 and x<-2 (we can summarise as x<=-2)
If you follow this procedure for every modulus question, you should be fine.