Odpowiedź:
I sposób

log72 = log(32 · 23) = log32 + log23 =
= 2log3 + 3log2 = 2a + 3b

II sposób

log 72 = log(2 · 36) = log2 + log62 =
= log2 + 2log6 = log2 + 2(log2 + log3) =
=  3log2 + 2log3 = 3b + 2a