杭州交通信息网教学评语:高数中的问题
来源：百度文库 编辑：杭州交通信息网 时间：2024/04/30 20:45:04
The lengths of the sides of a square are increasing at a constant rate of 2 feet/min.In term of the perimeter,p,what is the rate of change of the area of the square in square feet per minute?
A.p B.-p C.2p D.4p E.8p
A.p B.-p C.2p D.4p E.8p
let length of each side be s
perimeter be p
and area be A
A=s^2
dA/dt = 2s (ds/dt)
since s=p/4 and ds/dt=2
dA/dt=2(p/4)(2)=p
the answer's A