Помогите пожалуйста!!! Вычисли:

log15 27 = b
log15 27 = log15 3^3 = 3*log15 3 = 3* 1\log3 15 =
= 3\log3 (3*5) = 3\(log3 3 + log3 5) = 3\(1 + log3 5) = b
3 = b*(1 + log3 5)
1 + log3 5 = 3\b
log3 5 = 3\b - 1 = (3-b)\b

log15 5 = 1\log5 15 = 1\log5 (5*3) = 1\(log5 5 + log5 3) = 1\(1 + log5 3) =
= 1\(1 + 1\log3 5) = log3 5 \ (log3 5 + 1) =
= (3-b)\b \ ((3-b)\(b + 1) =
= (3-b)\b * (b+1)\(3-b) =
= (b+1)\b