Calculus AB help guys

Take the area of a circle A as a function of its radius r,

A(r) = π r ²

Differentiate A with respect to time t :

dA/dt = 2π r dr/dt

At the moment the circumference is 20π m, the radius is increasing at a rate of dr/dt = 0.2 m/s. Recall that circumference is equal to 2π times the radius, so the radius at this moment is (20π m) / (2π) = 10 m.

Then the area is changing at a rate of

dA/dt = 2π (10 m) (0.2 m/s) = 4π m²/s

-12 > a

step-by-step explanation:

-11 > 1 + a

subtract 1 from each side

-11 -1> 1 -1+ a

-12 > a