To find \((f \circ g)(x)\), we need to substitute the function \(g(x)\) into the function \(f(x)\).
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We have:
- \(f(x) = 0.04x\)
- \(g(x) = x - 4000\)
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Now, calculate \((f \circ g)(x)\): \[ (f \circ g)(x) = f(g(x)) = f(x - 4000) \] \[ = 0.04(x - 4000) \] \[ = 0.04x - 0.04 \cdot 4000 \] \[ = 0.04x - 160 \]
Thus, \((f \circ g)(x) = 0.04x - 160\).
Interpretation
This expression \((f \circ g)(x) = 0.04x - 160\) represents the amount Sally earns in commission, after accounting for the fact that she does not earn commission on the first $4,000 in sales. The additional term \(-160\) reflects a deduction due to the $4,000 threshold generally indicating that she does not receive commission on sales below that level.
Domain
The domain of \((f \circ g)(x)\) is determined by the function \(g(x) = x - 4000\) since sales cannot be negative. Therefore, for Sally to earn a commission, her sales \(x\) should be at least $4,000, meaning:
\[ x \geq 4000 \]
So, the domain can be represented as \(x \geq 4000\).
Conclusion
The correct response is: \((f \circ g)(x) = 0.04x - 160\) represents the amount Sally earns in commission. The domain is \(x \geq 4000\).