\(\left(a-b\right)^2=a^2-2ab+b^2\)
\(\left(b-a\right)^2=b^2-2ab+a^2=a^2-2ab+b^2\)
Ta thấy: \(a^2-2ab+b^2=a^2-2ab+b^2\Rightarrow\left(a-b\right)^2=\left(b-a\right)^2\)
Ta có :
\(\left(a-b\right)^2=a^2-2ab+b^2\left(1\right)\)
\(\left(b-a\right)^2=b^2-2ab+a^2\left(2\right)\)
Từ ( 1 ) ; ( 2 )
\(\Rightarrow\left(a-b\right)^2=\left(b-a\right)^2\)
Vậy \(\left(a-b\right)^2=\left(b-a\right)^2\)