Tìm các giá trị của x sao cho: a) |2x – 3| = |1 – x| b) x2 – 4x ≤ 5 c) 2x(2x – 1) ≤ 2x – 1. ai làm hộ mik nha !!! mik vote cho!! :)

Đáp án:

$\begin{array}{l}
a)\left| {2x - 3} \right| = \left| {1 - x} \right|\\
 \Leftrightarrow \left[ \begin{array}{l}
2x - 3 = 1 - x\\
2x - 3 = x - 1
\end{array} \right.\\
 \Leftrightarrow \left[ \begin{array}{l}
3x = 4\\
x = 2
\end{array} \right.\\
 \Leftrightarrow \left[ \begin{array}{l}
x = \dfrac{4}{3}\\
x = 2
\end{array} \right.\\
Vậy\,x = \dfrac{4}{3};x = 2\\
b){x^2} - 4x \le 5\\
 \Leftrightarrow {x^2} - 4x - 5 \le 0\\
 \Leftrightarrow \left( {x - 5} \right)\left( {x + 1} \right) \le 0\\
 \Leftrightarrow  - 1 \le x \le 5\\
Vậy\, - 1 \le x \le 5\\
c)2x\left( {2x - 1} \right) \le 2x - 1\\
 \Leftrightarrow 2x\left( {2x - 1} \right) - \left( {2x - 1} \right) \le 0\\
 \Leftrightarrow \left( {2x - 1} \right)\left( {2x - 1} \right) \le 0\\
 \Leftrightarrow {\left( {2x - 1} \right)^2} \le 0\\
 \Leftrightarrow 2x - 1 = 0\\
 \Leftrightarrow x = \dfrac{1}{2}\\
Vậy\,x = \dfrac{1}{2}
\end{array}$