\(E=4\left(x^2+\dfrac{3}{2}x+\dfrac{1}{4}\right)\)
\(=4\left(x^2+2\cdot x\cdot\dfrac{3}{4}+\dfrac{9}{16}-\dfrac{5}{16}\right)\)
\(=4\left(x+\dfrac{3}{4}\right)^2-\dfrac{5}{4}>=-\dfrac{5}{4}\)
Dấu '=' xảy ra khi x=-3/4
\(F=9\left(x^2-\dfrac{16}{9}x+\dfrac{7}{9}\right)\)
\(=9\left(x^2-2\cdot x\cdot\dfrac{8}{9}+\dfrac{64}{81}-\dfrac{1}{81}\right)\)
\(=9\left(x-\dfrac{8}{9}\right)^2-\dfrac{1}{9}>=-\dfrac{1}{9}\)
Dấu '=' xảy ra khi x=8/9
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