`5-(x-6)=4(3-2x)`
`<=> 5-x+6 = 12 - 8x`
`<=> 11-x -12 +8x =0`
`<=> 7x - 1=0`
`<=> 7x =1 => x=1/7`
vậy `S ={1/7}`
`3-x(1-3x)=5(1-2x)`
`<=> 3-x+3x^2 = 5-10x`
`<=> 3 - x +3x^2 -5+10x=0`
`<=>9x +3x^2 -2 =0`
ta có `Delta = 9^2 - 4.3.(-2) = 105 >0`
`=> `PT có 2 nghiệm phân biệt`
\(\left\{{}\begin{matrix}x_1=\dfrac{-b+\sqrt{\Delta}}{2.a}=\dfrac{-9+\sqrt{105}}{6}\\x_2=\dfrac{-b-\sqrt{\Delta}}{2.a}=\dfrac{-9-\sqrt{105}}{6}\end{matrix}\right.\)
a: =>12-8x=5-x+6=11-x
=>-7x=-1
hay x=1/7
b: \(\Leftrightarrow3-x+3x^2=5-10x\)
\(\Leftrightarrow3x^2-x+3-5+10x=0\)
\(\Leftrightarrow3x^2+9x-2=0\)
\(\text{Δ}=9^2-4\cdot3\cdot\left(-2\right)=81+24=105>0\)
Do đó: PT có 2 nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{-9-\sqrt{105}}{6}\\x_2=\dfrac{-9+\sqrt{105}}{6}\end{matrix}\right.\)
