若limx→∞[(x-α)/(x+α)]x=2,则α=_____.
-(1/2)ln2 分析:2=limx→∞[(x+α-2α)/(x+α)]x=limx→∞[1+-2α/(x+α)]x+α-α =limx→∞{[1+-2α/(x+α)]-(x+α)/2α}-2α•[1+-2α/(x+α)]-α=e-2α, 所以-2α=ln2,即α=-(1/2)1n2.
若limx→∞[(x-α)/(x+α)]x=2,则α=_____.
-(1/2)ln2 分析:2=limx→∞[(x+α-2α)/(x+α)]x=limx→∞[1+-2α/(x+α)]x+α-α =limx→∞{[1+-2α/(x+α)]-(x+α)/2α}-2α•[1+-2α/(x+α)]-α=e-2α, 所以-2α=ln2,即α=-(1/2)1n2.