Question

6x - (2x+5) (3x-2)=7

Answer 1

`6x-(2x+5)(3x-2)=7`

`<=>6x-(6x^{2}+15x-4x-10)-7=0`

`<=>6x-6x^{2}-11x+10-7=0`

`<=>-6x^{2}-5x+3=0`

`<=>x^{2}+(5)/(6)x-(1)/(2)=0`

`<=>[x^{2}+2.x.(5)/(12)+((5)/(12))^{2}]-(97)/(144)=0`

`<=>(x+(5)/(12))^{2}=(97)/(144)`

`<=>x+(5)/(12)=(+-\sqrt{97})/(12)`

`<=>x=(-5+-\sqrt{97})/(12)`

Vậy `S={(-5+\sqrt{97})/(12);(-5-\sqrt{97})/(12)}`

Answer 2

`6x - 6x^2 - 11x + 10 = 7`

`-6x^2 - 5x + 3 =0`

`-> \Delta= 25 + 72 = 97 > 0`

`-> x = (5 +-sqrt97)/12`.

Answer 3

`6x - 6x^2 + 11x - 10 = 7`

`-6x^2 + 17x - 17 =0`

`\Delta = 17^2 - 4 . 6 . 17 = -119 < 0`

`->` Ptr vô nghiệm