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Equations and inequalities with modulus

Geometric meaning of xa|x-a|
The number xa|x-a| is the distance on the coordinate line from xx to the fixed point aa (no sign: always 0\geq0). Standard rewrites follow: • xa<b, b>0|x-a|<b,\ b>0 ↔ the point xx is closer than bb to aa ↔ a double linear inequality ab<x<a+ba-b<x<a+b. • xa>b, b>0|x-a|>b,\ b>0two rays: x<abx<a-b or x>a+bx>a+b. When b=0b=0, xa0|x-a|\leq0 gives the single point x=ax=a.
When splitting cases do not forget b>0b>0; if the right-hand side is negative you often get "no solution" or the whole line — check the context
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