Answer:
5 feet
Explanation:
We are told that the height of the dome can be modelled by the equation:

The question is essentially asking us: for what value of d will the value of h be 50 feet?
To solve this, we have to substitute h in the equation with 50 and then solve for d.
∴

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This means that 5 feet from the center of the dome, the height of the dome is 50 feet.