Question

英语数学高数题求助

Answer 1

带入两个t[2，5] 到轨迹方程S
Si=[-2, 77.5 ]
ds=79.5
dt=5-2=3
V=80/3=26.5

Answer 2

s= t^3-1.5t^2 -2t

v
=ds/dt
=3t^2-3t -2
average velocity over [2,5]

=(1/3)∫(2->5) (3t^2-3t -2) dt
=(1/3)[ t^3-1.5t^2 -2t]|(2->5)
=(1/3) [ (125-37.5-10)-(8-6-4) ]
=(1/3) (79.5)
=26.5
ans : E