Ta có
\(B=\frac{2x^2+2}{\left(x+1\right)^2}\\ =\frac{x^2+2x+1+x^2-2x+1}{\left(x+1\right)^2}\\ =\frac{\left(x+1\right)^2}{\left(x+1\right)^2}+\frac{\left(x-1\right)^2}{\left(x+1\right)^2}\\ =1+\frac{\left(x-1\right)^2}{\left(x+1\right)^2}\)
\(MinB=1\Leftrightarrow\left(x-1\right)^2=0\Leftrightarrow x=1\)