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a)
5.(12-x)-20=30
⇒60-5x-20=30
⇒-5x=30+20-60
⇒-5x=-10
⇒x=2
b)(17x - 25 ) : 8 + 65 = 92
(17x - 25 ) : 8 + 65 = 81
17x - 25 = 16 x 8 = 128
17x = 128+25=153
x= 153:17 =9
c)
x=23
Giải thích các bước giải:
3x – 10 = 2x + 13
3x-2x=13+10
x=23
d)4(2x+7)-3(3x-2)=24
4.2x+4.7-3.3x+3.2=24
8x+28-9x+6=24
8x-9x=24-28-6=-10
=>(-1)x=-10
x=-10:(-1)
x=10
a. \(5\cdot\left(12-x\right)-20=30\Leftrightarrow5\left(12-x\right)=50\)
\(\Leftrightarrow12-x=50:5=10\)
\(\Leftrightarrow x=12-10=2\)
b. \(\left(17x-25\right):8+65=9^2\)
\(\Leftrightarrow\left(17x-25\right):8=81-65=16\)
\(\Leftrightarrow17x-25=16:8=2\)
\(\Leftrightarrow17x=2+25=27\Leftrightarrow x=\frac{27}{17}\)
c. \(3x-10=2x+13\)
\(\Leftrightarrow3x-2x=10+13\)
\(\Leftrightarrow x=23\)
d. \(4\cdot\left(2x+7\right)-3\cdot\left(3x-2\right)=24\)
\(\Leftrightarrow8x+28-9x+6=24\)
\(\Leftrightarrow34-x=24\Leftrightarrow x=10\)
![](https://rs.olm.vn/images/avt/0.png?1311)
-12(x-5)+7(3-x)=5
-12x - (-60) + 21 - 7x = 5
- (12x+7x) + (60+21) = 5
-19x + 81 = 5
-19x = 5 - 81
-19x = -76
x = -76 : (-19)
x = 4
Ta có \(-12.\left(x-5\right)+7.\left(3-x\right)=5\)
\(\Rightarrow-12x+60+21-21x=5\)
\(\Rightarrow\left(-12x-21x\right)+\left(60+21\right)=5\)
\(\Rightarrow-33x+81=5\)
\(\Rightarrow-33x=-77\)
\(\Rightarrow x=\frac{7}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(72003 + 72002) : 72001
= 72002 . (7 + 1) : 72001
= 7 . 8
= 56
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1.
\(10^{28}+8=\left(10^3\right)^{25}+8=8^{25}.125^{25}+8⋮8\)
Mặt khác:
\(10^{28}+8=10^{28}-1+9=\left(10-1\right).A+9=9A+9⋮9\)
\(\)Mà \(\left(8;9\right)=1\Rightarrow10^{28}+8⋮72\)
![](https://rs.olm.vn/images/avt/0.png?1311)
|x|+12/45=4/5
=> |x|=4/5-12/45
=>|x|=24/45
=> x=24/45 hoac x=-24/45
![](https://rs.olm.vn/images/avt/0.png?1311)
ta có :91=7.13 vì (13,7)=1
ta chứng ming M chia hết cho 7 và 13 \(\Rightarrow\)M \(⋮\)91
CM M\(⋮\)7
CM M\(⋮\)13
\(\Rightarrow\)M\(⋮\)91
-7.[8-3.2-12:(-4)]-3
-7.[8-6-(-3)]-3
-7.[2-(-3)]-3
-7.5-3
-35-3
=-38
mik ko viết đề bài
ko ai help :(