Помогите решить 2 задание

Решите задачу:

$log_ {\pi^2}( \frac{a^2b}{ \pi ^3} )= \frac{1}{2} log_ {\pi}( \frac{a^2b}{ \pi ^3} ) =\frac{1}{2} (log_ {\pi}a^2b-log_ {\pi}\pi ^3} ) =\\ =\frac{1}{2} (log_ {\pi}a^2+log_ {\pi}b-3log_ {\pi}\pi} ) =\frac{1}{2} (2log_ {\pi}a+log_ {\pi}b-3)\\ log_{\pi} \sqrt{a} =3\\ \frac{1}{2} log_{\pi} a =3\\ log_{\pi} a =6\\ \frac{1}{2} (2log_ {\pi}a+log_ {\pi}b-3)=\frac{1}{2} (2*6+5-3)=7\\$

$3^{4x+5}=81\\ 3^{4x+5}=3^4\\ 4x+5=4\\ 4x=-1\\ x=- \frac{1}{4} =-0.25$