f(t)=limx趋近于无穷t*[(x+t)/(x-t)]的x次方,求f'(t)要详细过程谢谢

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/15 07:43:03

f(t)=limx趋近于无穷t*[(x+t)/(x-t)]的x次方,求f'(t)要详细过程谢谢
f(t)=limx趋近于无穷t*[(x+t)/(x-t)]的x次方,求f'(t)要详细过程谢谢

f(t)=limx趋近于无穷t*[(x+t)/(x-t)]的x次方,求f'(t)要详细过程谢谢
f(t)=lim t*[(x+t)/(x-t)]^x
=lim t*[1+2t/(x-t)]^[(x-t)/2t*2tx/(x-t)]
=lim t*e^[2tx/(x-t)]
=t*e^(2t)
f'(t)=e^(2t)+2te^(2t)
=(2t+1)e^(2t)

f(t)=lim(x→∞)t*(1+2t/(x-t))^x=lim(x→∞)t*[(1+1/(x/(2t)-1/2))^(x/(2t)-1/2)]^(2t)*(1+1/(x/(2t)-1/2))^t=t*e^(2t)*1^t=te^(2t)
f'(t)=e^(2t)+te^(2t)*2=e^(2t)(2t+1)