Question

Tìm nghiệm của đa thức sau: A\(\left(x\right)\)=\(^{2x^2-11x+5}\)

Answer 1

\(A\left(x\right)=2x^2-11x+5\)

\(A\left(x\right)=2x^2-x-10x+5\)

\(A\left(x\right)=x\left(2x-1\right)-5\left(2x-1\right)\)

\(A\left(x\right)=\left(2x-1\right)\left(x-5\right)\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=0\\x-5=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=5\end{matrix}\right.\)

Answer 2

\(A\left(x\right)=2x^2-11x+5=2\left(x^2-\dfrac{11}{2}x+\dfrac{5}{2}\right)=2\left(x^2-\dfrac{11}{2}x+\dfrac{121}{8}-\dfrac{101}{8}\right)=2\left(x-\dfrac{11}{4}\right)^2-\dfrac{101}{4}\ge-\dfrac{101}{4}\)