Đáp án + Giải thích các bước giải :
Ta có : `|A|=3-3x`
`<=>3-3x=[4(x-1)(x+1,5)]/(x-3)(xne3)`
`<=>[(3-3x)(x-3)]/(x-3)=[4(x-1)(x+1,5)]/(x-3)`
`=>(3-3x)(x-3)=4(x-1)(x+1,5)`
`<=>3x-9-3x^2+9x=4(x^2+1,5x-x-1,5)`
`<=>3x-9-3x^2+9x=4x^2+6x-4x-6`
`<=>3x-9-3x^2+9x-4x^2-6x+4x+6=0`
`<=>-7x^2+10x-3=0`
`<=>-7x^2+7x+3x-3=0`
`<=>-7x(x-1)+3(x-1)=0`
`<=>(x-1)(3-7x)=0`
`<=>`\(\left[ \begin{array}{l}x-1=0\\3-7x=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=1\\x=\dfrac{3}{7}\end{array} \right.\)`(tm)`
Vậy `S= {1;3/7}`.
