Exploration
Let \(y_{1}=a^{x}, y_{2}=\mathrm{NDER} y_{1}, y_{3}=y_{2} / y_{1},\) and
\(y_{4}=e^{y_{3}}\)
(a) Describe the graph of \(y_{4}\) for \(a=2,3,4,5 .\) Generalize your
description to an arbitrary \(a>1\)
(b) Describe the graph of \(y_{3}\) for \(a=2,3,4,\) 5. Compare a table of values
for \(y_{3}\) for \(a=2,3,4,5\) with \(\ln a\) . Generalize your description to an
arbitrary \(a>1\)
(c) Explain how parts (a) and (b) support the statement
\(\frac{d}{d x} a^{x}=a^{x} \quad\) if and only if \(\quad a=e\)
(d) Show algebraically that \(y_{1}=y_{2}\) if and only if \(a=e\) .