1.

Solve for x, |x + 1| + |x| >3 .

Answer»

On LHS of the given inequality, we have two terms both containing modulus. By equating the expression within the modulus to zero, we get x = -1,0 as critical points. These critical points divide the real line in three parts as (−∞, −1),[−1,0),[0. ∞).

Case - I :

When −∞ < x < −1

|x + 1| + |x| > 3 

⇒ −x− 1 − x > 3 

⇒ x < −2.

Case - II 

When −1 ≤ x < 0

x + 1| + |x| > 3 

⇒ x + 1 − x > 3 ⇒ 1 > 3

Case - III 

When 0 ≤ < ∞,

x + 1| + |x| > 3 

⇒ x + 1 + x > 3 

⇒ x > 1.

Combining the results of cases (I) (II) and (III), we get,

x ∈ (−∞, −2),∪ [1, ∞)



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