Question

Giúp

Answer 1

Lời giải:

$(a+b+c)^2=3(a^2+b^2+c^2)$

$\Leftrightarrow 2(ab+bc+ac)=2(a^2+b^2+c^2)$

$\Leftrightarrow (a^2-2ab+b^2)+(b^2-2bc+c^2)+(c^2-2ac+a^2)=0$

$\Leftrightarrow (a-b)^2+(b-c)^2+(c-a)^2=0$

$\Rightarrow a-b=b-c=c-a=0$

$\Rightarrow a=b=c$

Do đó:

$S=(a-a)^{1972}+(b-b+2)^2+(c-c-1)^{2021}=0+4+(-1)=3$