đáp án và chia ra từng câu 1

Giải thích các bước giải:

1) $x^2 - x = 0$
$
\begin{aligned}
& x(x - 1) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 1 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 1 \end{aligned} \right.
\end{aligned}
$

2) $x^2 - 4x = 0$
$
\begin{aligned}
& x(x - 4) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 4 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 4 \end{aligned} \right.
\end{aligned}
$

3) $x^2 + 3x = 0$
$
\begin{aligned}
& x(x + 3) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x + 3 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= -3 \end{aligned} \right.
\end{aligned}
$

4) $x + 5x^2 = 0$
$
\begin{aligned}
& x(1 + 5x) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 1 + 5x &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= -\dfrac{1}{5} \end{aligned} \right.
\end{aligned}
$

5) $x^2 - 7x = 0$
$
\begin{aligned}
& x(x - 7) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 7 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 7 \end{aligned} \right.
\end{aligned}
$

6) $3x^2 - 6x = 0$
$
\begin{aligned}
& 3x(x - 2) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} 3x &= 0 \\ x - 2 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 2 \end{aligned} \right.
\end{aligned}
$

7) $x^2 + 7x = 0$
$
\begin{aligned}
& x(x + 7) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x + 7 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= -7 \end{aligned} \right.
\end{aligned}
$

8) $7x^2 + 2x = 0$
$
\begin{aligned}
& x(7x + 2) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 7x + 2 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= -\dfrac{2}{7} \end{aligned} \right.
\end{aligned}
$

9) $x^2 + 6x = 0$
$
\begin{aligned}
& x(x + 6) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x + 6 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= -6 \end{aligned} \right.
\end{aligned}
$

10) $2x^2 - 5x = 0$
$
\begin{aligned}
& x(2x - 5) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 2x - 5 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= \dfrac{5}{2} \end{aligned} \right.
\end{aligned}
$

11) $3x^2 + 7x = 0$
$
\begin{aligned}
& x(3x + 7) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 3x + 7 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= -\dfrac{7}{3} \end{aligned} \right.
\end{aligned}
$

12) $5x - 3x^2 = 0$
$
\begin{aligned}
& x(5 - 3x) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 5 - 3x &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= \dfrac{5}{3} \end{aligned} \right.
\end{aligned}
$

13) $5x^2 - 13x = 0$
$
\begin{aligned}
& x(5x - 13) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 5x - 13 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= \dfrac{13}{5} \end{aligned} \right.
\end{aligned}
$

14) $-3x^2 + 5x = 0$
$
\begin{aligned}
& x(-3x + 5) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ -3x + 5 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= \dfrac{5}{3} \end{aligned} \right.
\end{aligned}
$

15) $3x^2 - 7x = 0$
$
\begin{aligned}
& x(3x - 7) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 3x - 7 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= \dfrac{7}{3} \end{aligned} \right.
\end{aligned}
$

16) $4x^3 - x = 0$
$
\begin{aligned}
& x(4x^2 - 1) = 0 \\
& x(2x - 1)(2x + 1) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ 2x - 1 &= 0 \\ 2x + 1 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= \dfrac{1}{2} \\ x &= -\dfrac{1}{2} \end{aligned} \right.
\end{aligned}
$

17) $x^3 - 4x = 0$
$
\begin{aligned}
& x(x^2 - 4) = 0 \\
& x(x - 2)(x + 2) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 2 &= 0 \\ x + 2 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 2 \\ x &= -2 \end{aligned} \right.
\end{aligned}
$

18) $x^3 - 9x = 0$
$
\begin{aligned}
& x(x^2 - 9) = 0 \\
& x(x - 3)(x + 3) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 3 &= 0 \\ x + 3 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 3 \\ x &= -3 \end{aligned} \right.
\end{aligned}
$

19) $x^3 - 16x = 0$
$
\begin{aligned}
& x(x^2 - 16) = 0 \\
& x(x - 4)(x + 4) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 4 &= 0 \\ x + 4 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 4 \\ x &= -4 \end{aligned} \right.
\end{aligned}
$

20) $x^3 - 25x = 0$
$
\begin{aligned}
& x(x^2 - 25) = 0 \\
& x(x - 5)(x + 5) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} x &= 0 \\ x - 5 &= 0 \\ x + 5 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 5 \\ x &= -5 \end{aligned} \right.
\end{aligned}
$

21) $4x^3 - 36x = 0$
$
\begin{aligned}
& 4x(x^2 - 9) = 0 \\
& 4x(x - 3)(x + 3) = 0 \\
\Leftrightarrow \quad & \left[ \begin{aligned} 4x &= 0 \\ x - 3 &= 0 \\ x + 3 &= 0 \end{aligned} \right. \Leftrightarrow \left[ \begin{aligned} x &= 0 \\ x &= 3 \\ x &= -3 \end{aligned} \right.
\end{aligned}
$