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a)3x - 105 : 21 = 19
3x - 5 = 19
3x = 19 + 5
3x = 24
x = 24 : 8
x = 3
b, x - 7 = 14 - 3 . 23
x - 7 = 14 - 3 . 8
x - 7 = 14 - 24
x - 7 = -10
x = (-10) + 7
x = -3
HT và $$$
Bài 2:
a) 3x - 105 : 21= 19 b) x - 7= 14 - 3 . 2^3
3x - 5 = 19 x - 7= 14 - 3.8
3x = 19+ 5 x - 7= 14 - 24
3x = 24 x - 7= -10
x = 24 : 3 x = -10+7
x = 8 x = -3

\(a.97-7\left(x-8\right)=3\cdot2^4\)
\(97-7\left(x-8\right)=48\)
\(7\left(x-8\right)=97-48\)
\(7\left(x-8\right)=49\)
\(x-8=49:7=7\)
\(x=7+8=15\)
\(b.5x^2-74=51\)
\(5x^2=51+74=125\)
\(x^2=125:5=25\)
\(\Rightarrow x=\pm5\)
\(c.3x+2-3x=216\)
\(0x=214\)
⇒ \(x\in\) rỗng
\(5\left(3x-4\right)^3=40\)
\(\left(3x-4\right)^3=40:5=8\)
⇒ 3x - 4 = 2
⇒ 3x = 2 + 4 = 6
⇒ x = 6 : 3 = 2
a.97−7(x−8)=3⋅24
\(97 - 7 \left(\right. x - 8 \left.\right) = 48\)
\(7 \left(\right. x - 8 \left.\right) = 97 - 48\)
\(7 \left(\right. x - 8 \left.\right) = 49\)
\(x - 8 = 49 : 7 = 7\)
\(x = 7 + 8 = 15\)
\(b . 5 x^{2} - 74 = 51\)
\(5 x^{2} = 51 + 74 = 125\)
\(x^{2} = 125 : 5 = 25\)
\(\Rightarrow x = \pm 5\)
\(c . 3 x + 2 - 3 x = 216\)
\(0 x = 214\)
⇒ \(x \in\) rỗng
\(5 \left(\left(\right. 3 x - 4 \left.\right)\right)^{3} = 40\)
\(\left(\left(\right. 3 x - 4 \left.\right)\right)^{3} = 40 : 5 = 8\)
⇒ 3x - 4 = 2
⇒ 3x = 2 + 4 = 6
⇒ x = 6 : 3 = 2

2x - 3 = 17
2x = 17 + 3
2x = 20
x = 20 : 2
x = 10
---------------
4² - 3x = 27.3 - 77
16 - 3x = 81 - 77
16 - 3x = 4
3x = 16 - 4
3x = 12
x = 12 : 3
x = 4
----------------
48 + 2x = 3.2³
48 + 2x = 3.8
48 + 2x = 24
2x = 24 - 48
2x = -24
x = -24 : 2
x = -12
----------------
(13x - 12²) : 5 = 5
13x - 144 = 5.5
13x - 144 = 25
13x = 25 + 144
13x = 169
x = 169 : 13
x = 13
\(2x-3=17\)
\(2x=17+3\)
\(2x=20\)
\(x=20:2\)
\(x=10\)
____
\(4^2-3x=27.3-77\)
\(16-3x=81-77\)
\(16-3x=4\)
\(3x=16-4\)
\(3x=12\)
\(x=12:3\)
\(x=4\)
_____
\(48+2x=3.2^3\)
\(48+2x=3.8=24\)
\(2x=24-48\)
\(2x=\left(-24\right)\)
\(x=\left(-24\right):2\)
\(x=\left(-12\right)\)
____
\(\left(13x-12^2\right):5=5\)
\(\left(13x-144\right):5=5\)
\(13x-144=5.5\)
\(13x-144=25\)
\(13x=25+144\)
\(13x=169\)
\(x=169:13\)
\(x=13\)



\(2^5=32;;;;;;;;;;;3^4=81\)
42+(3x+7):2=32+81
(3x+7):2=113-42
(3x+7):2=71
3x+7=71*2
3x+7=142
3x=142-7
3x=135
x=135:3
x=45

3\(x\) - 42 = 3.23
3\(x\) - 42 = 3.8
3\(x\) - 42 = 24
3\(x\) = 24 + 42
3\(x\) = 66
\(x\) = 66: 3
\(x\) = 22
3x - 42 = 3 . 23
3x - 42 = 3 . 8
3x - 42 = 24
3x = 24 + 42
3x = 66
x = 66 : 3
=> x = 22.