已知a,b,c≥0,且a+b+c=1,求证1/(a^2+a+1)+1/(b^2+b+1)+1/(c^2+c+1)≥7/3

已知a、b、c是非零实数,且a^2+b^2+c^2=1,a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)=-3,求a+b+c的值 a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)=-3 a(1/b+1/c)+1+b(1/c+1/a)+1+c(1/a+1/b)+1=-3+3 a(1/a+1/b+1/c