Giải toán 8 tập 1: Câu 50 sgk trang 23

a) \(x(x - 2) + x - 2 = 0\)
\(\Leftrightarrow (x - 2) (x + 1) = 0\)
\(\Rightarrow \left[\begin{array}{l}x - 2 = 0 \\ x + 1 = 0 \end{array} \right.\)
\(\Leftrightarrow \left[\begin{array}{l} x = 2 \\ x = -1 \end{array} \right.\)
b) \(5x(x - 3) - x + 3 = 0\)
\(\Leftrightarrow 5x ( x - 3) - (x - 3) = 0\)
\(\Leftrightarrow (x - 3) (5x - 1) = 0\)
\(\Rightarrow \left[\begin{array}{l}x - 3 = 0 \\ 5x - 1 = 0 \end{array} \right.\)
\(\Leftrightarrow \left[\begin{array}{l} x = 3 \\ 5x = 1 \end{array} \right.\)
\(\Leftrightarrow \left[\begin{array}{l} x = 3 \\ x = \dfrac{1}{5} \end{array} \right.\)

Lưu ý: \(A.B = 0 \Leftrightarrow A = 0 \) hoặc \(B = 0\)