9514 1404 393
Answer:
increasing 7/24 ft per week
Step-by-step explanation:
An expression for the length of the base can be written from the Pythagorean theorem relation between the sides of the triangle.
If the height is 7-x, where x is the number of weeks after the height is 7 feet, then the base length is ...
b = √(25^2 -(7-x)^2) = √(625 -(49 -14x +x^2)) = √(-x^2 +14x +576)
Then the rate of change of b with respect to x is ...
b' = (-2x +14)/(2√(-x^2 +14x +576))
When x=0, the rate of change of the base is ...
b' = 14/(2√576) = 7/24
The base is increasing 7/24 ft per week when the height is 7 ft.
