limx→0ax+bx−cx−dxx
=limx→0(ax−1)+(bx−1)−(cx−1)+(dx−1)x
=limx→0ax−1x+limx→0bx−1x−limx→0cx−1x−limx→0dx−1x
=log a+log b−log c−log d
=log(abcd)
limx→0ax−a−xx
limx→0ax+bx−2x
limx→0ax+a−x−2x2