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Bài 9:
a) 15x + 40 = 15 + 20.8
15x + 40 = 15 + 160
15x + 40 = 175
15x = 175 - 40 = 135
x = 135 / 15 = 9
b) ( x-1 )( 5-x ) = 0
=> x-1 = 0 hoặc 5-x = 0
+) x-1 = 0 +) 5-x = 0 ( còn lại tự làm nhé ^^ )
c) x - 140 : 35 = 270
x - 140 = 270 . 35 = 9450
x = 9450 + 140 = 9590
d) ( 14 - 3x ) + ( 6 + x ) = 0
14 - 3x + 6 + x = 0
( 14 + 6 ) - ( 3x -x ) = 0
20 - 2x = 0
2x = 20
x = 10
b. 1404 : [118 - (4x + 6)] = 27
118 - (4x + 6) = 52
4x + 6 = 66
4x = 60
x = 15
d) \(5x^2-3x=0\)
\(\Leftrightarrow x\left(5x-3\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\5x-3=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{3}{5}\end{cases}}\)
e) \(3\left(x-1\right)+4\left(x-1\right)^2=0\)
\(\Leftrightarrow\left(x-1\right)\left[3-4.\left(x-1\right)\right]=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\3-4\left(x-1\right)=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=1\\4\left(x-1\right)=3\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=1\\x-1=\frac{3}{4}\Rightarrow x=\frac{7}{4}\end{cases}}\)
f) \(2\left(x-2\right)^2=\left(x-2\right)\)
\(\Leftrightarrow\orbr{\begin{cases}x-2=0\\2\left(x-2\right)-1=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=2\\x-2=\frac{1}{2}\Rightarrow x=\frac{5}{2}\end{cases}}\)
g) \(\left(x-2020\right)^4=\left(x-2020\right)^2\)
\(\Leftrightarrow\orbr{\begin{cases}\left(x-2020\right)^2=0\\\left(x-2020\right)^2-1=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=2020\\x=2019,x=2021\end{cases}}\)
a,x/9=5/3 = x=15
b,17/x=85/105 = x = 21
c,6/8=15/x = x = 20
d,x/8=2/3 = x = 6
Bài 1: Tìm x biết
a) x - 50 : 25 = 8
x- 2 = 8
x= 8+2
x=10
b) (x + 40).15 = 75.24
x+40 = 75.24:15
x+40 = 70
x= 30
c) (x - 32) - 15 = 0
x- 31 = 15
x= 15+ 31
x = 46
d) 1234 : x = 2
x= 1234:2
x = 617
e) (x - 34).26 = 0
x- 34 = 0: 26
x= 0 + 34
x= 34
f) 152 + (x + 231) : 2 = 358
(x+231):2 = 358- 152
(x+231):2 = 206
x+ 231 = 206*2
x= 412 - 231
x= 181
1.
a) x - 50 : 25 = 8
x - 2 = 8
x = 10
b) (x + 40) . 15 = 75 . 24
x + 40 = 75 . 24 : 15
x + 40 = 120
x = 80
c) (x - 32) - 15 = 0
x - 32 = 15
x = 47
d) 1234 : x = 2
x = 617
e) (x - 34) . 26 = 0
Thỏa mãn điều kiện x - 34 = 0
x = 34
f) 152 + (x + 231) : 2 = 358
(x + 231) : 2 = 206
x + 231 = 412
x = 181
2.
a) 45 . (2 . x - 4) . 13 = 0
Thỏa mãn điều kiện 2 . x - 4 = 0
x = 2
b) 5 . x - 38 : 19 = 13
5 . x - 2 = 13
5 . x = 15
x = 3
c) 100 - 3 . (8 + x) = 1
3 . (8 + x) = 99
8 + x = 33
x = 25
d) [(x + 12) - 17] : 5 = 4
(x + 12) - 17 = 20
x + 12 = 37
x = 25
e) 84 - 4 . (2 . x + 1) = 48
4 . (2 . x + 1) = 36
2 . x + 1 = 9
2 . x = 8
x = 4
a) (x – 45).27 = 0 ó x – 45 = 0 ó x = 45
b) 41.(2x – 8).13 = 0 ó 2x – 8 = 0 ó x = 4
c) (x – 36):18 = 12 ó x – 36 = 12.18 ó x = 216 + 36 ó x = 252
d) 43.(x – 18) = 86 ó x – 18 = 86:43 ó x = 2+18 ó x = 20
e) 96 : (121 – x) = 4 ó 121 – x = 96 : 4 ó 121 – x = 24 ó x = 121 – 24 ó x = 97
f) 340 : (15x+5) = 17 ó 15x + 15 = 340 :17 ó 15x + 5 = 20 ó 15x = 20 – 5 ó 15x = 15 ó x = 1
a) (x - 12).105= 0 b) 47. (27 - x) = 94 c) 2x + 69.2 = 69.5
--> x - 12 = 0: 105 --> 27 - x = 94 : 47 = 2 --> 2x + 138 = 345
--> x - 12 = 0 --> 27 - x = 2 --> 2x = 345 - 138
--> x = 0 + 12 --> x = 27 - 2 --> 2x = 207
--> x = 12 --> x = 25 --> x = 207 : 2
vậy x = 12 vậy x bằng 25 --> x = 103,5
vậy x = 103,5
d) (x - 7).(2x - 8)= 0 e) (x + 1)+(x + 2)+...+(x + 10)= 165
--> x - 7 = 0 hoặc 2x - 8 = 0 ( x + x + .... + x ) + ( 1 + 2 + 3 + ..... + 10 ) = 165
--> x = 0 + 7 hoặc 2x = 0 + 8 10x + 52 = 165
--> x = 7 hoặc x = 8 : 2 10x = 165 - 52
--> x = 7 hoặc x = 4 10x = 113
vậy x = 7 hoặc x = 4 x = 113 : 10
x = 11,3
vậy x = 11,3
1,
a,\(2020-\left(249+2020\right)+\left(249-573\right)\)
\(=2020-249-2020+249-573\)
\(=-573\)
b,\(\left|-257\right|+\left(-3\right)^0-\left(18+257\right)\)
\(=257+1-18-257\)
\(=1-18=-17\)
\(c,25.\left(85-47\right)-85.\left(47+25\right)\)
\(=25.85-25.47-47.85+85.25\)
\(=85.\left(25-47+25\right)-25.47\)
\(=85.3-25.47\)
\(=-920\)
2,
\(a,15-5.\left(x+2\right)=-30\)
\(=>5.\left(x+2\right)=15+30=45\)
\(=>x+2=\frac{45}{5}=9\)
\(=>x=7\)
\(b,\left(x+2\right)^2+5=105\)
\(=>\left(x+2\right)^2=100\)
\(=>\left(x+2\right)^2=10^2\)
\(=>x+2=10\)
\(=>x=8\)
\(c,\left|2x-5\right|-\left(-6\right)=11\)
\(=>\left|2x-5\right|=11-6=5\)
\(=>\orbr{\begin{cases}2x-5=5\\2x-5=-5\end{cases}}\)
\(=>\orbr{\begin{cases}2x=5-5=0\\2x=-5+5=0\end{cases}=>x=0}\)
\(a,3^n=3^4\)
\(\Rightarrow n=4\)
\(b,2008^n=2008^0\)
\(\Rightarrow n=0\)
Bài 2:
Ta có: \(11^{1979}< 11^{1980}=1331^{660}\)
\(37^{1320}=37^{2\cdot660}=1369^{660}\)
mà \(1331^{660}< 1369^{660}\)
nên \(11^{1979}< 37^{1320}\)
a) \(\left(27-x\right).45=0\Rightarrow27-x=0\Rightarrow x=27\)
b) \(15x+40=15+20.8\Rightarrow15x+40=175\Rightarrow15x=135\Rightarrow x=9\)
c) \(\left(x-1\right).2020=2020\Rightarrow x-1=1\Rightarrow x=2\)
d) \(6x+3x-4x=105\Rightarrow5x=105\Rightarrow x=21\)
e) \(x+\left(x+1\right)+\left(x+2\right)+...+\left(x+100\right)=5151\)
\(\Rightarrow101x+\left(1+2+...+100\right)=5151\)
Ta có \(1+2+...+100=\left(1+100\right)+\left(2+99\right)+...+\left(50+51\right)\)
\(=101\times50=5050\)
\(\Rightarrow101x+5050=5151\Rightarrow101x=101\Rightarrow x=1\)