Using a calculator or computer, sketch the graph of
y = 2 e^x + 4 e^{-x}
for -3 \le x \le 3 , 0\le y\le 20 .
Observe that it looks like the graph of y=\cosh x .

Approximately where is its minimum?

Minimum at

Show algebraically that

*(Think what this tells you about the graph you
obtained!)*

You can earn partial credit on this problem.