limx→08x−4x−2x+1x2
=limx→04x(2x−1)−(2x−1)x2
=limx→0(2x−1)(4x−1)x2
=limx→0(2x−1x)×limx→0(4x−1x)
=log 2.log 4=log 2(log22)
=log 2(2 log2)=2(log 2)2
limx→08x−2xx