tolong bantu beserta caranya ya kak ......

5log3= a, ==\» log3/log5 = a
15log81 = log81 / log15
= log3^4 / log3.5
= 4. log3 / (log3 + log5). Beri bilangan pokok baru 3 , sehingga
= 4. 3log3/ ( 3log3 + 3log5
= 4 / (1 + 1/a)
=4 / {( a + 1)/a }
= 4a / (a + 1)