Решение 

 

 

 

 

 

 

 

Проверка 

> solve(log[`+`(25, `-`(`*`(9, `*`(`^`(x, 2)))))](`+`(625, `-`(`*`(81, `*`(`^`(x, 4)))))) = `+`(2, `/`(1, `*`(log[3](`+`(25, `-`(`*`(9, `*`(`^`(x, 2))))))))))
 

`+`(`*`(`/`(5, 6), `*`(`^`(2, `/`(1, 2))))), `+`(`-`(`*`(`/`(5, 6), `*`(`^`(2, `/`(1, 2)))))) (62.2.1)