Solve the following inequalities
(i)
> 2
(ii)
≤ 1
(iii)
> 1
(iv)|x 2 + 3x| + x 2 – 2 ≥ 0
(v) |x + 3| > |2x – 1|
Text Solution
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(i) 1 +
> 2 or 1 +
< –2 ⇒
> 0 or
< 0
⇒ 0 < x < 3 or –1 < x < 0 ⇒ x ∈ (–1, 0) ∪ (0, 3)
(ii) –1 ≤
≤ 1 ⇒
≥ 0 and
≤ 0
⇒
≥ 0 and
≥ 0
x ∈ (– ∞ , –4] ∪ (–2, 1] ∪ (2, ∞ ) and x ∈ (– ∞ , –2) ∈ [–1, 2) ∪ [4, ∞ )
Taking intersection we get x ∈ (– ∞ , –4] ∪ [–1, 1] ∪ [4, ∞ )
(iii) case-I x ≥ –3 ⇒
> 0
⇒
> 0 ⇒ x ∈ (– ∞ , –2) ∪ (–1, ∞ ) But x ≥ – 3 ⇒ x ∈ [–3, –2) ∪ (–1, ∞ )
case-II: x < –3 ⇒
> 0 ⇒
< 0 ⇒ –5 < x < –2
But x < –3 ⇒ x ∈ (–5, –3) ∴ x ∈ (–5, –2) ∪ (–1, ∞ ).
(iv) |x 2 + 3x| + x 2 – 2 ≥ 0
case-I: x < – 3
⇒ 2x 2 + 3x – 2 ≥ 0 ⇒ (2x – 1) (x + 2) ≥ 0 ⇒ x ∈ (– ∞ , – 2) ∪ 
But x < – 3 ⇒ x ∈ (– ∞ , – 3) ....(i)
case-II– 3 ≤ x < 0
⇒ 3x + 2 ≤ 0 ⇒ x ≤ – 
But – 3 ≤ x < 0 ⇒ x ∈
....(ii)
case-III: x ≥ 0
⇒ 2x 2 + 3x – 2 ≥ 0 ⇒ x ∈
....(iii)
union of (i), (ii) and (iii) gives (i) ∪ (ii) ∪ (iii)
x ∈
∪ 
(v) |x + 3| > |2x –1| ⇒ x 2 + 9 + 6x > 4x 2 + 1 – 4x
⇒ 3x 2 – 10x – 8 < 0 ⇒
(x – 4) < 0 ⇒ –
< x < 4
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