Cho 1/x+1/y+1/z=0 (x; y; z khác 0). Chứng minh rằng: 1/x^2+1/y^2+1/z^2=3/xyz

Cho 1/x+1/y+1/z=0 (x; y;z khác 0)
CMR: 1/x^2+1/y^2+1/z^2=3/xyz