If you mean,
[tex]0.61^{2x + 1} = 39[/tex]
then the answer is going to be
[tex]x = \frac{log39}{2log \: 0.61} - \frac{1}{2} [/tex]
but if you mean,
[tex]0.61 ^{2} x + 1[/tex]
then, the answer is going to be, x = 102.123085.
