高等数学 不等式问题 十万火急 急急急急急急急急急急!!!!!!!!! 悬赏100先,解决完美200+!!!

2025-04-28 10:52:40
推荐回答(1个)
回答1:

考虑1
改写题目,设loga=x logb=y logc=z 1
y/x+z/y+x/z<= x/y+y/z+z/x

y+x<=z+y

(z-y)(y+x)(y-x)<=(z-y)(z+y)(y-x)

(z-y)(y^2-x^2)<=(z^2-y^2)(y-x)

z(y^2-x^2)-y(y^2-x^2)<=y(z^2-y^2)-x(z^2-y^2)

z(y^2-x^2)+x(z^2-y^2)<=y(z^2-y^2)+y(y^2-x^2)

z(y^2-x^2)+x(z^2-y^2)<=y(z^2-x^2)

两边除xyz

(y^2-x^2)/xy+(z^2-y^2)/zy<=(z^2-x^2)/xz

(y/x-x/y=(y^2-x^2)/xy,其馀同理)

y/x-x/y+z/y-y/z<=z/x-x/z

移项得证

y/x+z/y+x/z<=x/y+y/z+z/x