A new office building in town has x² + 4 floors. Each floor is 3x² – 5 feet high. Which expression shows the total height of this office building?
3x⁴ – 20 feet
4x² – 1 feet
3x⁴ + 7x² – 20 feet
4x⁴ + 6x² – 20 feet
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To find the total height of the office building, we need to multiply the number of floors by the height of each floor.
The number of floors is given by (x^2 + 4), and the height of each floor is (3x^2 – 5).
So, the total height (H) can be calculated as:
[
H = (text{number of floors}) times (text{height of each floor})
]
[
H = (x^2 + 4)(3x^2 – 5)
]
Now let’s expand this expression:
1. Distribute (x^2):
[
x^2 cdot 3x^2 = 3x^4
]
[
x^2 cdot (-5) = -5x^2
]
2. Distribute (4):
[
4 cdot 3x^2 = 12x^2
]
[
4 cdot (-5) = -20
]
3. Combine all the results:
[
H = 3x^4 + (-5x^2 + 12x^2) – 20
]
[
H = 3x^4 + 7x^2 – 20
]
Thus, the expression showing the