Hello, Dave!
In a computer game, the motion of a car is enhanced by showing headlights on a building
when the car approaches the building. .The headlights form a parabola on the road.
As the car approaches the building, the beam narrows.
The equation of the parabola is: $\displaystyle y \:= \:x^2  4x +c,$ where $\displaystyle c < 0$ and $\displaystyle \frac{dc}{dt} = 14$
The xaxis represents the wall. Length is measured in meters and time in seconds.
Determine the rate at which the width of the beam is narrowing when $\displaystyle c = 14$
I agree completely with Captain Black. Code:

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The width of the beam is the distance between the two xintecepts.
I have the same steps as the Captain . . . and the same answer.
I don't see how we could have misread the problem.