[(1-log6 3)^2+log6 2-log6 18]/log6 4
=[(log6 6-log6 3)^2+log6 2-log6 (2*9)]/log6 (2^2)
=[(log6 6/3)^2+log6 2-(log6 2 +log6 9)]/(2*log6 2)
=[(log6 2)^2+log6 2-log6 2-log6 9]/(2*log6 2)
=[(log6 2)^2-log6 9]/(2*log6 2)
=(log6 2)/2-log6 3/log6 2
=(log6 2)/2-log2 3