Giải từ câu b bài 2 với hết bài 3 nhanh giúp e nha mn ơi

Đáp án + Giải thích các bước giải:

Bài 2:

a) $4x - 2 =x  + 5$

$\Leftrightarrow 4x - x = 2 + 5$

$\Leftrightarrow 3x = 7$

$\Leftrightarrow x = \dfrac{7}{3}$

Vậy $S = $`{7/3}`

b) $-2x - 5 = 5x - 7$

$\Leftrightarrow -2x - 5x = 5 - 7$

$\Leftrightarrow -7x = -2$

$\Leftrightarrow x = \dfrac{2}{7}$
Vậy $S = $`{2/7}`

c) $2(2x - 1) = 5(x - 1)$

$\Leftrightarrow 4x - 2 = 5x - 5$

$\Leftrightarrow 4x - 5x = 2 - 5$

$\Leftrightarrow -x = -3$

$\Leftrightarrow x = 3$

Vậy $S = $`{3}`

d) $5(1 - 3x) = -2(4x + 5)$

$\Leftrightarrow 5 - 15x = -8x - 10$

$\Leftrightarrow 8x - 15x = -5 - 10$
$\Leftrightarrow -7x = -15$

$\Leftrightarrow x =\dfrac{15}{7}$

Vậy $S = $`{15/7}`

Bài 3:

a) $\dfrac{x}{2} - \dfrac{1}{5} = 2 - \dfrac{x}{3}$

$\Leftrightarrow 3x - \dfrac{6}{5} = 12 - 2x$

$\Leftrightarrow 3x + 2x = 12 + \dfrac{6}{5}$

$\Leftrightarrow 5x = \dfrac{66}{5}$

$\Leftrightarrow x =\dfrac{66}{25}$

Vậy $S = $`{66/25}`

b) $1 - \dfrac{x + 5}{3} = \dfrac{3(x - 1)}{4}$

$\Leftrightarrow 12 - 4(x + 5) = 9(x - 1)$
$\Leftrightarrow 12 - 4x - 20 = 9x - 9$

$\Leftrightarrow -4x - 8 = 9x - 9$
$\Leftrightarrow -4x - 9x = 8 - 9$
$\Leftrightarrow -13x = -1$

$\Leftrightarrow x = \dfrac{1}{13}$

Vậy $S = $`{1/13}`

c) $\dfrac{6(x - 2)}{7} - 12 = \dfrac{2(x - 7)}{3}$

$\Leftrightarrow 18(x - 2) - 252 = 14(x - 7)$

$\Leftrightarrow 18x - 36 - 252 = 14x - 98$

$\Leftrightarrow 18x - 288 = 14x - 98$

$\Leftrightarrow 18x - 14x = 288 - 98$

$\Leftrightarrow 4x = 190$

$\Leftrightarrow x = \dfrac{95}{2}$

Vậy $S = $`{95/2}`

d) $\dfrac{7 - 2x}{2} - \dfrac{2}{5}(2 - x) = 1\dfrac{1}{4}$

$\Leftrightarrow 5(7 - 2x) - 4(2 - x) = 10 . \dfrac{5}{4}$

$\Leftrightarrow 35 - 10x - 8 + 4x = \dfrac{25}{2}$

$\Leftrightarrow 27 - 6x = \dfrac{25}{2}$

$\Leftrightarrow 6x = \dfrac{29}{2}$
$\Leftrightarrow x = \dfrac{29}{12}$
Vậy $S = $`{29/12}`