Chứng minh rằng: (x1 + x2 + x3)^2/(x2 + x3 + x4)^2 = x1^2 + x2^2 + x3^3/x2^2 + x3^3 + x4^4

Cho (x2)^2=x1.x3;(x3)^2=x2.x4.Chứng minh rằng: (x1+x2+x3)^2/(x2+x3+x4)^2=x1^2+x2^2+x3^3/x2^2+x3^3+x4^4