2/π ≈ 0.637 m/s
the rate of change of area with respect to time is
a = πr²
da/dt = 2πr·dr/dt
filling in given values in the above equations, we can find r and dr/dt.
25π = πr² ⇒ r = 5
20 = 2π·5·dr/dt
dr/dt = 20/(10π) = 2/π . . meters per second
the radius is increasing at the rate of 2/π ≈ 0.637 meters per second.
centre = (2, 6)
the centre is at the midpoint of the diameter.
use the midpoint formula to find the centre
centre = [(- 2 + 6), (8 + 4)] = (2, 6)
y = 100 is the easiest function with these points.
another one is
y = (x - 2)(x - 3) + 100 = x^2 - 5·x + 106