Answer:
, 
Step-by-step explanation:
The velocity function of the projectile is obtained by deriving the position function:

Now, the velocities after 3 and 15 seconds are, respectively:




<span>675890 is spelled six hundred and seventy-five thousand, eight hundred and ninety </span>
Hello,
y=2xe^x
y'=2(e^x+xe^x)=2(x+1)e^x
y''=2(e^x+(x+1)e^x)=2(x+2)e^x
x |-infinite -2 0 +infinite
e^x | ++++++++++++++++++
x+2 |------------0 +++++++++++
y'' | -----------0 +++++++++++
y''<0 if x<-2
<span>The interval on which the graph is concave down is (-infinite -2[</span>
Point A, point C, point B, and point E