Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}
{x^4} - 2\left( {m + 1} \right){x^2} + 2m + 1 = 0 \Leftrightarrow \left[ \begin{array}{l}
{x^2} = 1\\
{x^2} = 2m + 1
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = \pm 1\\
x = \pm \sqrt {2m + 1} \,voi\,m > - \frac{1}{2}\,do\,pt\,co\,4\,nghiem\,phan\,biet
\end{array} \right.\\
Gia\,su\,A\left( {{x_1};0} \right),C\left( {{x_3};0} \right)\\
\Rightarrow {S_{ACK}} = 4 \Leftrightarrow \frac{1}{2}d\left( {K,AC} \right).AC = 4\\
\Leftrightarrow \frac{1}{2}.2.\sqrt {{{\left( {{x_3} - {x_1}} \right)}^2}} = 4 \Leftrightarrow {\left( {{x_3} - {x_1}} \right)^2} = 16\\
\Leftrightarrow {\left( {\sqrt {2m + 1} + 1} \right)^2} = 16 \Leftrightarrow \left[ \begin{array}{l}
\sqrt {2m + 1} + 1 = 4\\
\sqrt {2m + 1} + 1 = 4\,\left( {vo\,nghiem} \right)
\end{array} \right.\\
\Leftrightarrow \sqrt {2m + 1} = 3 \Leftrightarrow 2m + 1 = 9 \Leftrightarrow m = 4
\end{array}\)
