a)1/2×x-3/2=7/4 b)(x-1/2)×(-4)=-1/4

a) `1/2x-3/2=7/4`

`→1/2x=7/4+3/2`

`→1/2x={13}/4`

`→x={13}/4:1/2`

`→x={13}/2`

b) `(x-1/2).(-4)={-1}/4`

`→x-1/2={-1}/4:(-4)`

`→x-1/2=1/{16}`

`→x=1/{16}+1/2`

`→x=9/{16}`

Đáp á+Giải thích các bước giải:

 a) $\dfrac{1}{2}$ $\times$ $x$ -$\dfrac{3}{2}$ = $\dfrac{7}{4}$

$\dfrac{1}{2}$ $\times$ $x$ = $\dfrac{7}{4}$ + $(-\dfrac{3}{2})$

$\dfrac{1}{2}$ $\times$ $x$ = $\dfrac{1}{4}$

$x$ = $\dfrac{1}{4}$ : $\dfrac{1}{2}$

$x$ = $\dfrac{1}{2}$

Vậy $x$ = $\dfrac{1}{2}$

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b) ($x$ - $\dfrac{1}{2})$ $\times$ (-4) = $\dfrac{-1}{4}$

$x$ - $\dfrac{1}{2}$ = $\dfrac{-1}{4}$ : (-4)

$x$ - $\dfrac{1}{2}$ = $\dfrac{1}{16}$

$x$ = $\dfrac{1}{16}$ + $\dfrac{1}{2}$

$x$ = $\dfrac{9}{14}$

Vậy $x$ = $\dfrac{9}{14}$