Question

alguem sabe fazer? mudança de base

Answer 1

$A = \log_35 \cdot \log_{25}81\\ A = \log_35 \cdot \log_{5^2}3^4\\ A = \log_35 \cdot 4\log_{5^2}3\\\\ A = \frac{\log5}{\log3} \cdot \frac{4\log3}{\log5^2}\\ A = \frac{\log5}{\log3} \cdot \frac{4\log3}{2\log5}\\ </strong><strong>A = \frac{\cancel{\log5}}{</strong><strong>\bcancel</strong><strong>\{log3}} \cdot \frac{4\bcancel{\log3}}{2\</strong><strong>\cancel{</strong><strong>log5}}\\\\</strong></p><p><strong>A = \frac{4}{2}\\\\ A = 2$

Sendo assim, letra C).