Cho (a + b + c)^2 = 3 (a^2 + b^2 + c^2)

Cho (a+b+c)^2=3(a^2+b^2+c^2)
Tính A=`2021a+b/a+b` + `2021b+c/b+c` + `2021c+a/c+a`