The inverse would make the inputs the outputs (switching the x's and y's) because plugging in 4 into the inverse would somehow output 4 and 5, the inverse could not exist. plug in the inverse points to see that the vertical line test would fail.
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>
