a: \(=x^2-x+\dfrac{1}{4}+\dfrac{3}{4}=\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}>=\dfrac{3}{4}\)
Dấu '=' xảy ra khi x=1/2
c: \(=8\left(x^2-x+\dfrac{7}{4}\right)\)
\(=8\left(x^2-x+\dfrac{1}{4}+\dfrac{3}{2}\right)\)
\(=8\left(x-\dfrac{1}{2}\right)^2+12>=12\)
Dấu '=' xảy ra khi x=1/2
d: \(=x^2+x+\dfrac{1}{4}+\dfrac{7}{4}=\left(x+\dfrac{1}{2}\right)^2+\dfrac{7}{4}>=\dfrac{7}{4}\)
Dấu '=' xảy ra khi x=-1/2
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