Ta có: \(A=x^2+x+10\)
\(=x^2+2.x.\dfrac{1}{2}+\dfrac{1}{4}-\dfrac{1}{4}+10\)
\(=\left(x+\dfrac{1}{2}\right)^2+\dfrac{39}{4}>0\)
-> ĐPCM.
ta có:
A=x2+x+10
=x2 +2x.\(\dfrac{1}{2}\)+\(\dfrac{1}{4}-\dfrac{1}{4}+10\)
=\(\left(x+\dfrac{1}{2}\right)^2+\dfrac{39}{4}>0\)
\(\RightarrowĐPCM\)
Vì \(A=x^2+x+10\)
\(\Leftrightarrow x^2+2x.\dfrac{1}{2}+\dfrac{1}{4}-\dfrac{1}{4}+10\)
\(\Leftrightarrow\left(x+\dfrac{1}{2}\right)^2+\dfrac{39}{4}>0\)
Tương tự ta có: ĐPCM