Question

Difficulty: MediumReal Numbers, Number Line, and Absolute Value

If xx and yy are real numbers such that ∣x−3∣≤2|x - 3| \le 2 and ∣y+1∣≤4|y + 1| \le 4, which of the following could be the value of ∣x−y∣|x - y|? Select all such values.

  1. A
    −2-2
  2. 00Answer
  3. 55Answer
  4. 1010Answer
  5. E
    1212

Answer

The possible values of ∣x−y∣|x - y| are 0, 5, and 10.
Solving the inequalities yields 1≤x≤51 \le x \le 5 and −5≤y≤3-5 \le y \le 3. The expression ∣x−y∣|x - y| represents the distance between xx and yy on the number line. Because the intervals overlap between 1 and 3, xx and yy can be equal, making the minimum distance 0. The maximum distance occurs at the extreme points x=5x = 5 and y=−5y = -5, giving a distance of ∣5−(−5)∣=10|5 - (-5)| = 10. Therefore, any value from 0 to 10 inclusive is possible, making 0, 5, and 10 valid values.

Step-by-Step Solution

1
Solve the absolute value inequality for xx.
−2≤x−3≤2  ⟹  1≤x≤5-2 \le x - 3 \le 2 \implies 1 \le x \le 5
Unwrapping ∣x−3∣≤2|x - 3| \le 2 gives the bounds for xx on the real number line.
2
Solve the absolute value inequality for yy.
−4≤y+1≤4  ⟹  −5≤y≤3-4 \le y + 1 \le 4 \implies -5 \le y \le 3
Unwrapping ∣y+1∣≤4|y + 1| \le 4 gives the bounds for yy on the real number line.
3
Determine the minimum and maximum possible values for ∣x−y∣|x - y|.
Minimum value is 0 (since the intervals [1,5][1, 5] and [−5,3][-5, 3] overlap at [1,3][1, 3]). Maximum value is ∣5−(−5)∣=10|5 - (-5)| = 10. Thus, 0≤∣x−y∣≤100 \le |x - y| \le 10.
The absolute value ∣x−y∣|x - y| represents the distance between xx and yy on the number line, which can take any real value from 0 to 10.
4
Evaluate the given choices against the range [0,10][0, 10].
The values 0, 5, and 10 fall within [0,10][0, 10], whereas −2-2 is impossible for absolute values and 1212 exceeds the maximum bound.
Determines which specific options are valid outcomes for ∣x−y∣|x - y|.

Key Concept

Absolute value as distance on the real number line and range of differences between bounded real variables
Estimated Time:1m 30s
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