Remember: logax=b⇒ab=x
in which "a" is the base of the log.
log4 (1/16) = 4^-2 = 1/4^2 = 1/16
4 to the power of -2 is equal to 1/16.
To answer this question, the equation in exponential form of "log4 (1/16) = -2" is " 4^-2 " (4 to the power of -2). :D