Tìm x : a) 2x. (3x-1) - 6x.(x+2) =42 b) 2x. (12x-5) - 8x . ( 3x-1) = 30 c) 3x. ( 3- 2x ) + 6x . ( x-1 ) = 15 Mik cần gấp . , mik sẽ vote 5 sao . Cảm ơn nhiều

`a)``2x(3x-1)-6x(x+2)=42`

`<=>6x^2-2x-6x^2-12x=42`

`<=>-2x-12x=42`

`<=>-44x=42`

`<=>x=-42/44`

`b)``2x(12x-5)-8x(3x-1)=30`

<=>24x^2-10x-24x^2+8=30`

`<=>-10x+8=30`

`<=>-10x=22`

`<=>x=-22/10`

`c)``3x(3-2x)+6x(x-1)=15`

`<=>9x-6^2+6x^2-6x=15`

`<=>9x-6x=15`

`<=>3x=15`

`<=>x=5`