Question

帮忙解道数学题

帮忙解道数学题：The area of an oil spill is increasing at a rate of 25t ft^2/s t seconds after the spill.Between times t=2 and t=4 the area of the spill increases by_____

Answer 1

dS/dt=25t => dS=25tdt 两边同时积分，得S1-S0=25/2*(t1^2-t2^2)=25/2*(16-4)=150 ft^2
其中S1表示t1=4时的面积，S0表示t0=2时的面积。

Answer 2

25*(4-2)=50 ft^2

Answer 3

能用中文吗