Question

Chứng minh:

Answer 1

xϵR

Answer 2

\(x^2+2x+3>0\\ \Leftrightarrow\left(x^2+2x+1\right)+2>0\\ \Leftrightarrow\left(x+1\right)^2+2>0\left(luôn.đúng\forall x\in R\right)\)

Vậy \(\forall x\in R\) thì \(x^2+2x+3>0\)

Answer 3

x^2 +2x+3>0

<=> (x^2 +2x +1) +2 >0

<=>(x+1)^2 +2>0( luôn đúng)