Bài tập 27 trang 121 SGK Toán 10 NC

Bài tập 27 trang 121 SGK Toán 10 NC

a)

\(\begin{array}{l}
\left\{ {\begin{array}{*{20}{l}}
{5x - 2 > 4x + 5}\\
{5x - 4 < x + 2}
\end{array}} \right.\\
 \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x > 7}\\
{4x < 6}
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x > 7}\\
{x < \frac{3}{2}}
\end{array}} \right.
\end{array}\)

(vô nghiệm)

Vậy \(S = \emptyset \)

b)

\(\begin{array}{l}
\left\{ {\begin{array}{*{20}{l}}
{2x + 1 > 3x + 4}\\
{5x + 3 \ge 8x - 9}
\end{array}} \right.\\
 \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x <  - 3}\\
{3x \le 12}
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x <  - 3}\\
{x \le 4}
\end{array}} \right.\\
 \Leftrightarrow x <  - 3
\end{array}\)

Vậy \(S = \left( { - \infty ; - 3} \right)\)

-- Mod Toán 10