a) Ta có: \(x^2-6x+10\)
\(=x^2-6x+9+1\)
\(=\left(x-3\right)^2+1>0\forall x\)
b: Ta có: \(4x^2-20x+27\)
\(=4x^2-20x+25+2\)
\(=\left(2x-5\right)^2+2>0\forall x\)
c: Ta có: \(x^2+x+1\)
\(=x^2+2\cdot x\cdot\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{3}{4}\)
\(=\left(x+\dfrac{1}{2}\right)^2+\dfrac{3}{4}>0\forall x\)
d: Ta có: \(x^2+4x+y^2-6y+15\)
\(=x^2+4x+4+y^2-6y+9+2\)
\(=\left(x+2\right)^2+\left(y-3\right)^2+2>0\forall x\)
Đúng 2
Bình luận (0)
