log以根号2为底的2的对数+ log9 27 +1/4log4 1/16
=1+3/2+1/4×（-2）
=2又1/2-1/2
=2

log2根号下7/48+log2 12-1/2log2 42-1
=1/2log2 7-1/2log2 3-2+log2 3+2-1/2log2 7-1/2log2 3-1-1
=-2