limx趋于0(2^x-3^x)/x
=limx趋于0(2^x-1+1-3^x)/x
=limx趋于0(2^x-1)/x+limx趋于0(1-3^x)/x
=limx趋于0(xln2)/x+limx趋于0(-xln3)/x
=ln2-ln3
=ln2/3