Đáp án:
`x = -5/16`
`x = 8/9`
`x = -21/2`
`x ∈ { -3/4 ; -5/4 }`
Lời giải:
`a, 4x + 1/2 = -3/4`
`⇔ 4x = -3/4 - 1/2`
`⇔ 4x = -3/4 - 2/4`
`⇔ 4x = -5/4`
`⇔ x = -5/4 : 4`
`⇔ x = -5/4 . 1/4`
`⇔ x = -5/16`
Vậy `x = -5/16`
`b, -1 1/3 + 2x = 4/9`
`⇔ -4/3 + 2x = 4/9`
`⇔ 2x = 4/9 + 4/3`
`⇔ 2x = 4/9 + 12/9`
`⇔ 2x = 16/9`
`⇔ x = 16/9 : 2`
`⇔ x = 16/9 . 1/2`
`⇔ x = 8/9`
Vậy `x = 8/9`
`c, x/15 = -7/10`
`⇔ 10x = 15 . (-7)`
`⇔ 10x = -105`
`⇔ x = (-105) : 10`
`⇔ x = -21/2`
Vậy `x = -21/2`
`d, |x + 1| = 3/4 - 1/2`
`⇔ |x + 1| = 3/4 - 2/4`
`⇔ |x + 1| = 1/4`
`⇔` \(\left[ \begin{array}{l}x+1=\frac{1}{4}\\x+1=\frac{-1}{4}\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=\frac{1}{4} - 1 = \frac{1}{4} - \frac{4}{4} = \frac{-3}{4}\\x=\frac{-1}{4} - 1 = \frac{-1}{4} - \frac{4}{4} = \frac{-5}{4}\end{array} \right.\)
Vậy `x ∈ { -3/4 ; -5/4 }`
