If f(x)=axf(x) = a^xf(x)=ax, what is f(x+h)−f(x)h\frac{f(x+h) - f(x)}{h}hf(x+h)−f(x)?
ax(ah−1)/ha^x(a^h-1)/hax(ah−1)/h
ah−1a^h-1ah−1
axlnaa^x \ln aaxlna
ax+h/ha^{x+h}/hax+h/h