Cho x^2 + y^2 + z^2 = 10. Chứng tỏ P = (xy + yz + zx)^2 + (x^2 - yz)^2 + (y^2 - zx)^2 + (z^2 - xy)^2 = 100

Bài 8: 1/a +1/b +1/c= 1/abc
Cm: 1/a^2n+1 +1/b^2n+1 +1/c^2n+1 = 1/(a^2n+1 + b^2n+1 +c^2n+1)= 1/(a+b+c)^2n+1
b 1/x +1/y +1/z= 1/xyz thì
1/x^2009 + 1/y^2009 + 1/z^2009 =1/(x^2009 + y^2009 +z^2009)
Bài 6
x^2+y^2+z^2=10
Chứng tỏ P=(xy+yz+zx)^2+(x^2-yz)^2+(y^2-zx)^2+(z^2-xy)^2=100