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How does Cauchy's inequality work?

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How does Cauchy's inequality work?

cauchy's inequality is supposed to be:

(xy^3+yz^3+zx^3)(z+x+y) *is greater than or equal to* xyz(y+z+x)^2.

i don't get what it's supposed to be used for, and how it works. it just confuses me. please help!!!


Hi, it is the squared special instance n=3, x,y,z>=0,

(y1,y2,y3)=(sqrt( z ),sqrt( x ),sqrt( y )),

x*y =(sqrt(xyz)y,sqrt(xyz)z,sqrt(xyz)x),
x.y = sqrt(xyz)(y + z + x).

Given x=0, z=1, the inequality reads

y(1+y)>=0 and fails for 0>y>-1, so nonnegativity is necessary.


(x+y+z)\neq 0 it is innecesary and (x+y+z)=0 is trivial.

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