1 answer
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if x >= 0
|x| + |x+1| + |x+3| = x+x+1+x+3 = 3x+4 = 4
so x = 0
if -1 <= x < 0
|x| + |x+1| + |x+3| = -x + x+1 + x+3 = x+4 = 4
x=0 does not meet the condition
If -3 <= x < -1
|x| + |x+1| + |x+3| = -x + -(x+1) + x+3 = -x+2 = 4
x = -2
If x < -3
|x| + |x+1| + |x+3| = -x + -(x+1) + -(x+3) = -3x-4 = 4
x = -8/3 but that does not fit the condition
so only 0 and -2 are solutions