Bài 2:
a: \(x^2+x+1\)
\(=x^2+2\cdot x\cdot\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{3}{4}\)
\(=\left(x+\dfrac{1}{2}\right)^2+\dfrac{3}{4}>0\)
b: \(4x^2+4x+2=4x^2+4x+1+1=\left(2x+1\right)^2+1>0\)
c: \(\dfrac{1}{4}x^2+x+3=\dfrac{1}{4}x^2+x+1+2\)
\(=\left(\dfrac{1}{2}x+1\right)^2+2>0\)
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