Question

tìm GTNN của A= 4x²-4x+19

Answer 1

\(A=4x^2-4x+19=4x^2+4x+1+18=\left(2x+1\right)^2+18\ge18\)

\(minA=18\Leftrightarrow2x-1=0\Leftrightarrow x=\dfrac{1}{2}\)

Answer 2

\(A=4x^2-4x+19\)

\(=4x^2-4x+1+18\)

\(=\left(2x-1\right)^2+18\ge18\forall x\)

Dấu '=' xảy ra khi \(x=\dfrac{1}{2}\)