數學log的問題?

如題 我對log不太了解 請達人幫個忙 解給我看 謝!1.Slove: 1. log x(以3為底)=4-log(x 24)(以3為底) 2. ln x=1 ln(x-1)2.Find the value for log 5(以4為底).Round your answers to 5 decimal places.3.The radioactive element 碳14 has a half-life of 5730 years.the percentage of 碳14 in the remains of plants and animals can be used to determineage.archaeologists found that the linen wrapping from one of the DeadSea Scrolls had lost 33.2% of its　碳１４.how old was the linen wrapping?　
1. 使用這樣的符號: log(3

x) = log x(以3為底)　log(3

x) = 4 - log(3

x 24)　log(3

x) = log(3

3^4) - log(3

x 24)　log(3

x) = log(3

3^4 / (x 24))　去掉 log　x = 3^4 / (x 24)　x * ( x 24 ) = 81　x^2 24x - 81 = 0　( x - 3 ) * ( x 27 ) = 0　x = 3 or -27　但是真數必須