`a):`
`3x - 5 = 13`
`⇒ 3x=13+5`
`⇒ 3x = 18`
`x = 18/3`
`x = 6`
`b):`
`x(x - 2) + 4x - 8 = 0`
`⇔ x^2−2x+4x−8=0`
`⇔ x^2+2x−8=0`
`⇔` $\left[ \begin{array}{l}a+b=2\\ab=-8\end{array} \right.$
`⇔` $\left[ \begin{array}{l}-1,8\\-2,4\end{array} \right.$
`⇔` $\left[ \begin{array}{l}-1+8=7\\-2+4=2\end{array} \right.$
`⇔` $\left[ \begin{array}{l}a=-2\\b=4\end{array} \right.$
`⇔ (x−2)(x+4)`
$\left[ \begin{array}{l}x=2\\x=-4\end{array} \right.$
`c):`
`3 + 5/3 < x - 1/9`
`⇔ 9/3 + 5/3 < x - 1/9`
`⇔ 14/3 < x - 1/9`
`⇔ x - 1/9 > 14/3`
`x > 14/3 + 1/9`
`x > 42/9 + 1/9`
`x > 43/9`
Cho mình xin hay nhất nha bạn!!!!
@Drew Mclntyre
