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Math · Algebra 1

Chapter 2: Inequalities

Absolute Value Inequalities

Less than traps, greater than splits.

Lesson
3
Time
About 23 minutes
0 of 11 done

Step 1: Let's Learn

Read it, or press Listen and follow the words.

|x| < 5 means the distance is under 5, so x lies between −5 and 5. That is an "and".

Greater than

|x| > 5 means the distance exceeds 5, so x is below −5 or above 5. That is an "or".

A way to remember

Less than traps the values inside; greater than splits them to the outside.

A different centre

|x − 4| < 2 measures distance from 4, not zero, so the answer is centred on 4.

Less than gives an "and"

|x − 3| < 5 says the distance from 3 is under 5, so x is within 5 either way: −2 < x < 8. Less-than absolute value inequalities always give a single bounded interval.

Greater than gives an "or"

|x − 3| > 5 says the distance exceeds 5, so x is far out on either side: x < −2 or x > 8. Greater-than inequalities give two separate rays, never one interval.

A way to remember which is which

Less-than traps the values between two bounds; greater-than throws them apart. Thinking in terms of distance from a point makes the two cases follow from meaning rather than from a memorised rule.

The impossible and the trivial cases

|x| < −2 has no solution, since distance cannot be negative. And |x| > −2 is true for every x. Checking the sign of the right-hand side before splitting handles both cases instantly.

Step 2: Try It Yourself

Tap and try it out.

Test whether a value lies inside or outside the trap.
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3

Step 3: Watch an Example

One step at a time.

Watch Priya Handle Both Kinds

Priya solves |x| < 4 and then |x| > 4.

  1. Step 1

    For |x| < 4, the distance is under 4, so −4 < x < 4.

Step 4: Your Turn

Practice makes it stick.

Trapped

Problem 1 of 2

|x| < 6. What is the largest whole number solution?

Split

Problem 2 of 2

|x| > 6. What is the smallest whole number above the gap?

Inside or Outside

1 of 8

|x| < 3. Largest whole number solution?

2 of 8

|x| < 3. Smallest whole number solution?

3 of 8

|x| > 2. Smallest whole number above the gap?

4 of 8

|x − 4| < 2. What is the centre of the solution?

5 of 8

|x − 4| < 2. Largest whole number solution?

6 of 8

Match each inequality to the shape of its solution.

Tap a card on the left to start.

7 of 8

|x| > 0. Which single number fails? Give it.

8 of 8

|x| < −2. How many solutions?

Step 5: Quick Check

Show what you know.

Question 1 of 1

|x| < 8. Largest whole number solution?

What You Learned

  • Less than traps the solutions into one interval around the centre.
  • Greater than splits them into two intervals with a gap.
  • An absolute value below a negative has no solutions at all.