Question

Tìm Min A = x⁴ - x² +2x + 7

Answer 1

A=(\(x^4\)-2\(x^2\)+1)+(\(x^2\)+2x+1)+5

A=\((x^2-1)^2+(x+1 )^2+5\)\(\ge\)\(5\)

Dấu bằng xảy ra\(\Leftrightarrow\)\(\begin{cases} x^2-1=0\\ x+1=0 \end{cases} \)

\(\Leftrightarrow\)\(x=-1\)

Vậy Amin=5 \(\Leftrightarrow\)x=-1