第1个回答 2022-11-10
考虑函数
y1=x^(x+1),y2=(x+1)^x
取对数,相减:
z=(x+1)lnx-xln(x+1)
求导:
z'=lnx+(x+1)/x-ln(x+1)-x/(x+1)
=ln[x/(x+1)]+1+1/x-(x+1-1)/(x+1)
=ln(1-1/(x+1)]+1+1/x-1+1/(x+1)
≈-1/(x+1)+1/x+1/(x+1)
=1/x>0
z是增函数。
x=1,Y1=1^2=1,Y2=2^1=2,y1<y2;
x=2,y1=2^3=8,y2=3^2=9,y1<y2;
x=3,y1=3^4=81,y2=4^3=64,y1>y2
从x=3往后,都是y1>y2
所以60^61>61^60