`(x + 7)(5x - 6) = (4x + 1)(2x - 3)`
`⇒ x(5x - 6) + 7(5x - 6) = 4x(2x - 3) + (2x - 3)`
`⇔ 5x^2 - 6x + 35x - 42 = 8x^2 - 12x + 2x - 3`
`⇔ 5x^2 + 29x - 42 = 8x^2 - 10x - 3`
`⇔ 8x^2 - 10x - 3 - 5x^2 - 29x + 42 = 0`
`⇔ 3x^2 - 39x + 39 = 0`
`⇔ 3(x^2 - 13x + 13) = 0`
`⇒ x^2 - 13x + 13 = 0`
`⇔ x^2 - 2 . x . 13/2 + 169/4 - 169/4 + 52/4 = 0`
`⇔ (x - 13/2)^2 - 117/4 = 0`
`⇒ (x - 13/2)^2 = 117/4`
`⇒ x - 13/2 = ±\sqrt{117}/2`
`⇒ x = (\sqrt{117} + 13)/2 và x = (-\sqrt{117} + 13)/2 `
`text(Vậy phương trình có nghiệm)` `S = {(\sqrt{117} + 13)/2 ; (-\sqrt{117} + 13)/2 }`
