lim(x→2）(1/x-1/2)/x-2是怎么化简成lim(x→2）(2-x)/2x(x-2)

几道求极限的高数题,lim1/x(tanπx/(2x+1)) x→∞lim x(x^x-1)x→0+lim(x^x^x- lim(x→∞)[(a x^2)/x+1]+bx=lim(x→∞)(a x^2)+bx(x+1) / x+1=lim(x lim(x→0)ln(1-2x)/x lim(x→0)(1-x^2-e^-x)/sinx 极限lim(x→0)(1-2/x)^x lim(x→∞)[sinx/x+xsin(1/2x)] lim（x/（1+x^2））,x趋向无穷大 lim(arcsinx/x)(1/x^2)(x趋于0） 求lim(x→0)x cos 1/x lim(x→∞)x^2/ (3x-1)的极限 lim(sin(x^2*cos(1/x)))/x怎么做? lim x(x+2)/x^2 (x→oo) lim(x^2+1/x^2-2x)^x=?