Đáp án+Giải thích các bước giải:
`2(a+1).(b+1)=(a+b)(a+b+2)`
`<=>2(a+1).(b+1)-(a+b).(a+b+2)=0`
`<=>2.(a+1).(b+1)-2.(a+b)-(a+b)^2=0`
`<=>2.[(a+1).(b+1)-(a+b)]-(a+b)^2=0`
`<=>2.(ab+a+b+1-a-b)-(a+b)^2=0`
`<=>2ab+2-a^2-2ab-b^2=0`
`<=>2-a^2-b^2=0`
`<=>a^2+b^2=2`
Vậy `a^2+b^2=2`
