Range Math Example 3

Follow the full solution, then compare it with the other examples linked below.

Example 3

easy
Find the range of f(x)=โˆ’โˆฃxโˆฃ+4f(x) = -|x| + 4.

Solution

  1. 1
    Since โˆฃxโˆฃโ‰ฅ0|x| \geq 0, we have โˆ’โˆฃxโˆฃโ‰ค0-|x| \leq 0, so f(x)=โˆ’โˆฃxโˆฃ+4โ‰ค4f(x) = -|x| + 4 \leq 4.
  2. 2
    The maximum value is 44 (at x=0x = 0), and f(x)โ†’โˆ’โˆžf(x) \to -\infty as โˆฃxโˆฃโ†’โˆž|x| \to \infty. The range is (โˆ’โˆž,4](-\infty, 4].

Answer

(โˆ’โˆž,4](-\infty, 4]
The negative sign in front of the absolute value flips the V-shape downward, creating a maximum rather than a minimum.

About Range

The range of a function is the set of all actual output values that the function can produce for inputs in its domain.

Learn more about Range โ†’

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