Ta có:
\(2\left(a^2+b^2\right)=\left(a+b\right)^2\)
\(\Rightarrow2a^2+2b^2=a^2+2ab+b^2\)
\(\Rightarrow2a^2+2b^2-a^2-2ab-b^2=0\)
\(\Rightarrow a^2-2ab+b^2=0\)
\(\Rightarrow\left(a-b\right)^2=0\)
\(\Rightarrow a-b=0\)
\(\Rightarrow a=b\)
\(2\left(a^2+b^2\right)=\left(a+b\right)^2\)
\(2a^2+2b^2=a^2+2ab+b^2\)
\(2a^2-a^2+2b^2-b^2-2ab=0\)
\(a^2-2ab+b^2=0\)
\(\left(a-b\right)^2=0\)
\(a-b=0\)
\(a=b\)
2( a2 + b2 ) = ( a + b )2
⇒ 2a2 + 2b2 = a2 + 2ab + b2
⇒2a2 - a2 + 2b2 - b2 - 2ab = 0
⇒a2 - 2ab + b2 = 0
⇒(a - b)2 = 0
⇒ a - b = 0
⇒ a = b (đpcm)
