y=(3x^2-1)/(x+1)e^(2/x)的斜渐近线

2个回答

  • 设渐近线方程:y=kx+b

    则k=lim(x→∞)[(3x²-1)/(x-1)][e^(2/x)]/x

    =lim(x→∞)[(3x²-1)e^(2/x)]/[x(x-1)]

    =lim(x→∞)[(3-1/x²)e^(2/x)]/(1-1/x)

    =[(3-0)e^0]/(1-0)

    =3

    故b=lim(x→∞)(y-kx)

    =lim(x→∞)[(3x²-1)e^(2/x)/(x+1)]-3x

    =lim(x→∞)[(3x²-1)e^(2/x)-3x²-3x]/(x+1)

    =lim(x→∞)[3x²[e^(2/x)-1]-3x-e^(2/x)]/(x+1)

    =lim(x→∞){3x[e^(2/x)-1]-3-[e^(2/x)]/x}/(1+1/x)

    =lim(x→∞){3x·2/x-3-[e^(2/x)]/x}/(1+1/x)

    =lim(x→∞){6-3-[e^(2/x)]/x}/(1+1/x)

    =3

    故渐近线方程:y=3x+3