Đáp án + Giải thích các bước giải:
`c) 2x(x - 5) = (x - 5)^2 ` $\\$ `=> 2x(x - 5) = (x - 5)(x - 5) ` $\\$ `=> 2x(x - 5) - (x - 5)(x - 5) = 0` $\\$ `=> (x - 5)[2x - (x - 5)] = 0` $\\$ `=> (x - 5)(2x - x + 5) = 0` $\\$ `=> (x - 5)(x + 5) = 0 => `\(\left[ \begin{array}{l}x=5\\x=-5\end{array} \right.\)
Câu d đề lỗi
e) `2x(3 - 4x) - 5x^2(4x - 3) = 0 => -2x(4x - 3) - 5x^2(4x - 3) = 0` $\\$ `=> (4x - 3)(-2x - 5x^2) = 0 => (4x - 3).(-x)(2 + 5x) = 0 ` $\\$ `+) 4x - 3 = 0 => 4x = 3 => x = 3/4` $\\$ `+) -x = 0 => x = 0` $\\$ `+) 2 + 5x = 0 => 5x = -2 => x = -2/5`
f) `(x + 8)(x^2 - 1) = 0 => (x + 8)(x - 1)(x + 1) = 0`
+) x + 8 = 0 => x = -8
+) x - 1 = 0 => x = 1
+) x + 1 = 0 => x = -1
`g) x^2 - 5x = 6 => x^2 - 5x - 6 = 0 ` $\\$ `=> x^2 + x - 6x - 6 = 0 => x(x + 1) - (6x + 6) = 0` $\\$ `=> x(x + 1) - 6(x + 1) = 0` $\\$ `=> (x + 1)(x - 6) = 0` $\\$ `=>` \(\left[ \begin{array}{l}x=-1\\x=6\end{array} \right.\)
