Question

với a b c tùy ý.CMR: a^2 + b^2 + c^2 > hoặc = 2ab - 2ac + 2bc

Answer 1

a^2 + b^2 + c^2 -2ab + 2ac - 2bc=>0

(a-b)^2 + c^2 + 2ac - 2bc=>0

(a-b)^2 + 2c(a-b) + c^2=>0

{(a-b)^2 + c}^2 =>0

suy ra a^2 + b^2 + c^2 => 2ab - 2ac + 2bc(DPCM)

 

Answer 2

a^2+b^2+c^2-2ab+2ac-2bc=>0.

=(a-b)^2+c^2+2ac-2bc=>0.

=(a-b)^2+2c(a-b)+c^2=>0.

=(a-b)^2+c^2=>0.

=>a^2+b^2+c^2=>2ab-2ac+2bc(DPCM)

tk cho mk nha^-^

Answer 3

a^2+b^2+c^2-2ab+2ac-2bc=>0.

=(a-b)^2+c^2+2ac-2bc=>0.

=(a-b)^2+2c(a-b)+c^2=>0.

=(a-b)^2+c^2=>0.

=>a^2+b^2+c^2=>2ab-2ac+2bc