Cho tam giác ABC có A(-1; 1), B(0; 2), C(1; 1). Tr...

A

- Hướng dẫn giải

\(\begin{array}{l}
H\left( {a;b} \right),\overrightarrow {AH}  = \left( {a + 1;b - 1} \right)\\
\overrightarrow {BH}  = \left( {a;b - 2} \right),\overrightarrow {BC}  = \left( {1; - 1} \right),\overrightarrow {AC}  = \left( {2;0} \right)\\
\left\{ \begin{array}{l}
\overrightarrow {AC} .\overrightarrow {BH}  = 0\\
\overrightarrow {BC} .\overrightarrow {AH}  = 0
\end{array} \right. \Rightarrow \left\{ \begin{array}{l}
2a + 0\left( {b - 2} \right) = 0\\
1\left( {1 + a} \right) - 1\left( {b - 1} \right) = 0
\end{array} \right.\\
 \Rightarrow \left\{ \begin{array}{l}
a = 0\\
b = 2
\end{array} \right.
\end{array}\)