According to the logarithmic property of the base change, the corrected answer is option four or the last.
The logarithmic property of base change given that
loga (b) = logc (b) / logc (a)
Therefore, the same property applies to this problem and the correct expression for this question is:
y1 = log (x) / log (6)
y2 = log (x + 4) / log2