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If [tex]\( r(x) = 2 - x^2 \)[/tex] and [tex]\( w(x) = x - 2 \)[/tex], what is the range of [tex]\( (w \circ r)(x) \)[/tex]?

A. [tex]\( (-\infty, 0] \)[/tex]
B. [tex]\( (-\infty, 2] \)[/tex]
C. [tex]\( [0, \infty) \)[/tex]
D. [tex]\( [2, \infty) \)[/tex]


Sagot :

To determine the range of [tex]\((w \circ r)(x)\)[/tex], we need to understand the behavior and ranges of the individual functions [tex]\(r(x)\)[/tex] and [tex]\(w(x)\)[/tex].

### Step 1: Determine the Range of [tex]\(r(x)\)[/tex]

The function [tex]\(r(x)\)[/tex] is given by:
[tex]\[ r(x) = 2 - x^2 \][/tex]

- This is a quadratic function with a maximum value at [tex]\(x = 0\)[/tex], since the coefficient of [tex]\(x^2\)[/tex] is negative, making it a downward-opening parabola.
- At [tex]\(x = 0\)[/tex], we have [tex]\( r(0) = 2 - 0^2 = 2 \)[/tex].

As [tex]\(x \)[/tex] approaches [tex]\(\pm \infty\)[/tex], [tex]\(x^2\)[/tex] grows without bound, causing [tex]\(2 - x^2 \)[/tex] to tend towards [tex]\(-\infty\)[/tex].

Thus, the range of [tex]\(r(x)\)[/tex] is:
[tex]\[ (-\infty, 2] \][/tex]

### Step 2: Determine the Range of [tex]\(w(x)\)[/tex]

The function [tex]\(w(x)\)[/tex] is given by:
[tex]\[ w(x) = x - 2 \][/tex]

The function [tex]\(w(x)\)[/tex] is a linear function with a slope of 1. This function is defined for all real numbers [tex]\(x\)[/tex] and has no restrictions.

### Step 3: Determine the Range of the Composite Function [tex]\((w \circ r)(x)\)[/tex]

The composite function [tex]\((w \circ r)(x)\)[/tex] is:
[tex]\[ (w \circ r)(x) = w(r(x)) \][/tex]
[tex]\[ (w \circ r)(x) = r(x) - 2 \][/tex]
[tex]\[ (w \circ r)(x) = (2 - x^2) - 2 \][/tex]
[tex]\[ (w \circ r)(x) = 2 - x^2 - 2 \][/tex]
[tex]\[ (w \circ r)(x) = - x^2 \][/tex]

Now, let's determine the range of [tex]\(-x^2\)[/tex]. Since [tex]\(x^2 \geq 0\)[/tex] for all real numbers [tex]\(x\)[/tex], [tex]\(-x^2\)[/tex] will be [tex]\(\leq 0\)[/tex] for all real numbers [tex]\(x\)[/tex].

Thus, [tex]\(-x^2\)[/tex] can take on values from [tex]\(-\infty\)[/tex] to 0, inclusive. Therefore, the range of [tex]\((w \circ r)(x)\)[/tex] is:
[tex]\[ (-\infty, 0] \][/tex]

### Conclusion

The correct answer is:
[tex]\[ (-\infty, 0] \][/tex]
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