求lim[ln(x^2-x+1)/ln(x^10+x+1)](x趋向于正无穷)

3个回答

  • 推荐答案不严谨

    应该用

    lim[ln(x^2-x+1)/ln(x^10+x+1)]

    =lim ln[x^2(1-1/x+1/x^2)]/ln[x^10(1+1/x^9+1/x^10)]

    =lim [ln( x^2)+ ln(1-1/x+1/x^2) ]/[ln(x^10)+ln(1+1/x^9+1/x^10)]

    =lim [2lnx+ln(1-1/x+1/x^2)]/[10lnx+ln(1+1/x^9+1/x^10)]

    上下同除lnx

    =lim[2+ln(1-1/x+1/x^2)/lnx]/[10+ln(1+1/x^9+1/x^10)/lnx]

    然后取极限ln(1-1/x+1/x^2)/lnx->ln1/∞=0

    同理ln(1+1/x^9+1/x^10)/lnx->0

    所以极限=(2+0)/(10+0)

    =1/5