Tìm x. Giúp mình với ạ

2) $(x+1)^2 = x + 1 \qquad (x \geq -1)$

$\Leftrightarrow (x +1)^2 – (x +1) = 0$

$\Leftrightarrow (x +1)(x +1- 1) = 0$

$\Leftrightarrow x(x + 1) = 0$

$\Leftrightarrow \left[\begin{array}{l}x = 0 \\x = -1\end{array}\right. (nhận)$

3) $4- x = 2(x – 4)^2 \qquad (x \leq  4)$

$\Leftrightarrow 2(x – 4)^2 + (x – 4) = 0$

$\Leftrightarrow (x – 4)[2(x – 4) + 1] = 0$

$\Leftrightarrow (x -4)(2x – 7) = 0$

$\Leftrightarrow \left[\begin{array}{l}x = 4\quad (nhận)\\x = \dfrac{7}{2}\quad (loại)\end{array}\right.$

4) $x(y +1) – y = 1$

$\Leftrightarrow x(y+1) – (y +1) = 0$

$\Leftrightarrow (y+1)(x -1) = 0$

$\Leftrightarrow \left[\begin{array}{l}x = 1\\y = -1\end{array}\right.$

5) $(x^2 +1)(x – 2) + 2x = 4$

$\Leftrightarrow (x^2 +1)(x – 2) + 2(x -2)= 0$

$\Leftrightarrow (x -2)(x^2 + 3) = 0$

$\Leftrightarrow x – 2 = 0$

$\Leftrightarrow x = 2$