Đáp án:
4,a Ta có :
$ 5 – (10 – x) = 7 $
$=> 5 - 10 + x = 7$
$=> -5 + x = 7$
$=> x = 7 - (-5) = 7 + 5 = 12$
$b, 3 – (17 – x) = 289 – (36+ 289)$
$=> 3 - 17 + x = 289 - 36 - 289$
$=> -14 + x = -36$
$=> x = -36 - (-14) = -36 + 14 = 22
$c, 25 – (x +5) = -415 –(15 – 415)$
$=> 25 - x - 5 = -415 + 15 + 415$
$=> 20 - x = 15$
$=> x = 20 - 15 = 5$
$d, 34 + (21 – x) = (3747 – 30) – 3746$
$=> 34 + 21 - x = 3747 - 30 - 3746$
$=> 55 - x = -29$
$=> x = 55 - (-29) = 55 + 29 = 84$
$e, 3.(2 – x) + 5. (x - 6) = -98$
$=> 6 - 3x + 5x - 30 = -98$
$=> -24 + 2x = -98$
$=> 2x = -98 - (-24) = -98 + 24 = -74$
$=> x = -74 : 2 = -37$
$f, (x+ 7) . (x – 9) = 0$
=> \(\left[ \begin{array}{l}x+7=0\\x-9 = 0 \end{array} \right.\)
=> \(\left[ \begin{array}{l}x=-7\\x=9\end{array} \right.\)
$g, (6-x)^{3} = -8 $
$=> (6 - x)^{3} = (-2)^{3}$
$=> 6 - x = -2$
$=> x = 6 - (-2) = 6 + 2 = 8$
$h, ⎹ 3x +9⎹ -15 = 27$
$=> | 3x + 9 | = 27 + 15 = 42$
=> \(\left[ \begin{array}{l}3x+9=42\\3x+9=-42\end{array} \right.\)
=> \(\left[ \begin{array}{l}x=11\\x=-17\end{array} \right.\)
$k, 14 + x = 36 – x.$
$=> x + x = 36 - 14$
$=> 2x = 22$
$=> x = 22 : 2 = 11$
Giải thích các bước giải:
