Answer:
[tex]4=2^{5r+1}\quad :\quad r=\frac{1}{5}\quad \left(\mathrm{Decimal}:\quad r=0.2\right)[/tex]
[tex]\mathrm{Convert\:}4\mathrm{\:to\:base\:}2\\4=2^2\\2^2=2^{5r+1}\\*\mathrm{If\:}a^{f\left(x\right)}=a^{g\left(x\right)}\mathrm{,\:then\:}f\left(x\right)=g\left(x\right)\\2=5r+1\\\mathrm{Solve\:}\:2=5r+1:\quad r=\frac{1}{5}[/tex]
Hope this helps!!!
[tex]Sofia[/tex]
