2) log2(2 * 6 ^(2/3) / (a^5 * c^4)) =
= log2(2 * 6 ^(2/3)) - log2(a^5 * c^4) =
= log2(2) + log2(6 ^(2/3)) - log2(a^5) - log2(c^4) =
= 1 + log2(2^(2/3)) + log2(3^(2/3)) - 5*log2(a) - 4*log2(c) =
= 5/3 + 2/3 * log2(3) - 5*log2(a) - 4*log2(c);
3) log7(x) = -1/7 * log7(a) - 4 * log7(c) - log7(b)
log7(x) = log7(a^(-1/7)) - log7(c^4) - log6(b)
log7(x) = log7( a^(-1/7) / (c^4 * b))
x = a^(-1/7) / (c^4 * b)
x = 1 / (a^(1/7) * c^4 * b)