To find the cross-sectional area of the rectangular solid shipping container, we need to divide the volume polynomial \( V(x) = 24x^3 + 6x^2 - 9x \) by the height \( h(x) = 3x \). The cross-sectional area \( A(x) \) can be expressed as:
\[ A(x) = \frac{V(x)}{h(x)} \]
Let's perform the polynomial division of \( 24x^3 + 6x^2 - 9x \) by \( 3x \).
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Set up the division: \[ 24x^3 + 6x^2 - 9x \div 3x \]
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Divide the leading term:
- The leading term of the numerator is \( 24x^3 \) and the leading term of the denominator is \( 3x \).
- \( \frac{24x^3}{3x} = 8x^2 \).
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Multiply:
- Multiply \( 8x^2 \) by the entire divisor \( 3x \): \[ 8x^2 \cdot 3x = 24x^3 \]
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Subtract:
- Subtract \( 24x^3 \) from \( 24x^3 + 6x^2 - 9x \): \[ (24x^3 + 6x^2 - 9x) - (24x^3) = 6x^2 - 9x \]
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Repeat the process:
- Now divide \( 6x^2 \) by \( 3x \): \[ \frac{6x^2}{3x} = 2x \]
- Multiply \( 2x \) by \( 3x \): \[ 2x \cdot 3x = 6x^2 \]
- Subtract: \[ (6x^2 - 9x) - (6x^2) = -9x \]
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Repeat again:
- Now divide \( -9x \) by \( 3x \): \[ \frac{-9x}{3x} = -3 \]
- Multiply \( -3 \) by \( 3x \): \[ -3 \cdot 3x = -9x \]
- Subtract: \[ -9x - (-9x) = 0 \]
After completing these steps, the result of the polynomial division is:
\[ A(x) = 8x^2 + 2x - 3 \]
Thus, the cross-sectional area of the shipping container is:
\[ \boxed{8x^2 + 2x - 3} \]