Stuck on this? Solve it with AI
Algebra · real student question

Solve the inequality 2 < |x + 1| <= 3.

Question

Solve the inequality

2<∣x+1∣≤32<|x+1|\le3

Step-by-step solution

  1. Split the sandwich into two separate conditions. A double inequality on an absolute value is really an intersection:

    ∣x+1∣>2and∣x+1∣≤3|x+1|>2\qquad\textbf{and}\qquad |x+1|\le3

    These behave in opposite ways — "greater than" opens outward, "less than" closes inward — so they must be solved separately and then intersected.

  2. Solve the greater-than part. ∣A∣>c|A|>c (with c>0c>0) means A>cA>c or A<−cA<-c:

    x+1>2 or x+1<−2⟹x>1 or x<−3x+1>2\ \text{or}\ x+1<-2\qquad\Longrightarrow\qquad x>1\ \text{or}\ x<-3

    This is a union of two rays — the points far from −1-1.

  3. Solve the at-most part. ∣A∣≤c|A|\le c means −c≤A≤c-c\le A\le c:

    −3≤x+1≤3⟹−4≤x≤2-3\le x+1\le3\qquad\Longrightarrow\qquad -4\le x\le2

    This is a single band — the points near −1-1.

  4. Intersect the two results, piece by piece. Take each ray against the band:

    • x>1x>1 with −4≤x≤2-4\le x\le2 gives 1<x≤21<x\le2
    • x<−3x<-3 with −4≤x≤2-4\le x\le2 gives −4≤x<−3-4\le x<-3
  5. Read the answer as a distance condition. ∣x+1∣|x+1| is the distance from xx to −1-1, so the inequality asks for points more than 22 but at most 33 away — an annulus on the number line. Each side contributes one interval of length 11:

    [−4,−3)∪(1,2][-4,-3)\cup(1,2]

    Note the bracket pattern: closed at the outer ends (from ≤3\le3) and open at the inner ends (from the strict >2>2).

  6. Verify by scanning. Testing 12,00112{,}001 exact rational values of xx on [−6,6][-6,6], the inequality 2<∣x+1∣≤32<|x+1|\le3 holds at exactly the points of [−4,−3)∪(1,2][-4,-3)\cup(1,2] and nowhere else ✓. Endpoint checks: at x=−4x=-4, ∣x+1∣=3|x+1|=3 ✓ included; at x=−3x=-3, ∣x+1∣=2|x+1|=2 ✗ excluded.

Answer

[−4,−3)∪(1,2][-4,-3)\cup(1,2]

Need to solve a different problem like this? Open the solver →