Pregunta
TIME The expression \( \pi(r-3)^{2} \) represents the area covered by the hour hand on a clock in one rotation, where \( r \) is the radius of the entire clock. Write a polynomial that represents the area covered by the hour hand in one rotation.
Ask by Willis Stuart. in the United States
Jan 23,2025
Solución de tutoría real
Respuesta verificada por el tutor
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The area covered by the hour hand in one rotation is represented by the polynomial:
\[
\pi r^{2} - 6\pi r + 9\pi
\]
Solución
To write a polynomial that represents the area covered by the hour hand in one rotation, let's start by expanding the given expression:
\[
\pi(r - 3)^2
\]
**Step 1: Expand the Binomial**
\[
(r - 3)^2 = r^2 - 6r + 9
\]
**Step 2: Multiply by π**
\[
\pi(r^2 - 6r + 9) = \pi r^2 - 6\pi r + 9\pi
\]
**Final Polynomial**
\[
\pi r^2 - 6\pi r + 9\pi
\]
**Interpretation:**
- **\(\pi r^2\)**: Represents the area of the entire clock.
- **\(-6\pi r\)**: Adjusts for the length of the hour hand.
- **\(+9\pi\)**: Adds a constant area based on the adjustment.
So, the polynomial that represents the area covered by the hour hand in one rotation is:
\[
\boxed{\pi r^{2} - 6\,\pi\, r + 9\,\pi}
\]
Revisado y aprobado por el equipo de tutoría de UpStudy
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Beyond the Answer
To find the area covered by the hour hand, we start with the expression \( \pi(r-3)^{2} \). To expand this, we can use the formula for squaring a binomial: \( (a-b)^{2} = a^{2} - 2ab + b^{2} \). Here, let \( a = r \) and \( b = 3 \): \[ (r-3)^{2} = r^{2} - 2 \cdot r \cdot 3 + 3^{2} = r^{2} - 6r + 9. \] Now, we multiply this expansion by \( \pi \): \[ \pi(r-3)^{2} = \pi(r^{2} - 6r + 9) = \pi r^{2} - 6\pi r + 9\pi. \] Thus, the polynomial that represents the area covered by the hour hand in one rotation is: \[ \pi r^{2} - 6\pi r + 9\pi. \]
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