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>
The guy ran at a speed of 8.07783 MPH
Here's how I got my answer:
1 km/hr. = 0.621371
So, if you do 
you will get your answer: 8.07783 MPH
5^2 + 12^2 = c^2
25 + 144 = c^2
169 = c^2
take the square root of both sides
+ - 13 = c
Area of a triangle is 0.5(base x height)
Base = 320mi
Height= 270+210= 480mi
0.5(480 x 320) = 76,800 miles squared
The answer to the question is c
