求下列极限：1.lim(x→2)(x+2/x-2) 2.lim(x→0)4x^3-2x^2+x^2-2x)

解：3。lim(x→0)[(tanx-sinx)/x^3]=lim(x→0)[sinx(1-cosx)/(x³cosx)]
=lim(x→0){(sinx/x)*[sin(x/2)/(x/2)]²*[1/(2cosx)]}