Question

which expression is equivalent log8 4a (b-4/c4)

Answer 1

 (1): "c4"   was replaced by   "c^4". 

Unauthorized use of the imaginary unit "i" or syntax error in complex arithmetic expression

..... V whichressionisequivalentlog84a(b-4/c^4)
The symbol "i" is only allowed in complex arithmetic, for example:
     (3/5+7i)+(0.3-7.002i) 
     (5+77i)-(19/4-8i) 
     (240-22i)*(247/7+2.222i) 
     (33/5+99i)/(33/5-88i)