Đáp án:
Giải thích các bước giải:
a) `(3x - 5)(4x +2)= 0`
`⇔` \(\left[ \begin{array}{l}3x-5=0\\4x+2=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}3x=5\\4x=-2\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=\dfrac{5}{3}\\x=-\dfrac{1}{2}\end{array} \right.\)
Vậy `S={5/3;-1/2}`
b) `(3x-2)/(x+7) = (6x+1)/(2x-3)`
ĐK: `x \ne -7, x \ne 3/2`
`⇔ (3x-2)(2x-3)=(6x+1)(x+7)`
`⇔ 6x^2-9x-4x+6=6x^2+42x+x+7`
`⇔ 56x=-1`
`⇔ x=-1/56\ (TM)`
Vậy `S={-1/56}`
c) `|4x| = 2x + 12 `
TH1: `x \ge 0`
`4x=2x+12`
`⇔ 4x-2x=12`
`⇔ 2x=12`
`⇔ x=6\ (TM)`
TH2: `x<0`
`4x=-2x-12`
`⇔ 4x+2x=-12`
`⇔ 6x=-12`
`⇔ x=-2\ (TM)`
Vậy `S={-2;6}`
