Bài 1 : Cho \(\frac{1}{x}\)\(+\)\(\frac{1}{y}\)\(+\)\(\frac{1}{z}\)\(=0\)
CMR \(x^2+y^2+z^2=\left(x+y+z\right)^2\)
Bài 2 : Cho \(a,b,c\) đôi một khác nhau. CMR :
\(\frac{1}{\left(a-b\right)^2}\)\(+\frac{1}{\left(b-c\right)^2}\)\(+\frac{1}{\frac{\left(c-a\right)^2}{ }}=\frac{1}{\left(a-b\right)}+\frac{1}{b-c}+\frac{1}{c-a}\)
Bài 3 : Cho \(\frac{1}{a}+\frac{1}{b}+\frac{1}{c}=0.Tính \)
M =\(\frac{b+c}{a}+\frac{c+a}{b}+\frac{a+b}{c}\)