Question

Answer 1

\(1,\\ a,A=x^3+8-\left(x^2-1\right)\left(x-1\right)\\ A=x^3+8-x^3+x^2+x-1=x^2+x+7\\ b,A-13=x^2+x-6=0\\ \Leftrightarrow\left(x+3\right)\left(x-2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=2\end{matrix}\right.\\ 2\text{ và }3\)

Đã làm: - Hoc24

\(4,A=-2x^2+6x-6\\ A=-2\left(x^2-3x+\dfrac{9}{4}\right)-\dfrac{3}{2}\\ A=-2\left(x-\dfrac{3}{2}\right)^2-\dfrac{3}{2}\le-\dfrac{3}{2}\)

Dấu \("="\Leftrightarrow x=\dfrac{3}{2}\)