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a) \(3.5^2-27:3^2-5^2.4-18:3^2\)
\(=3.\left(5^2-5^2\right).27:\left(3^2-3^2\right)\)
\(=15.0.27.0\)
\(=0.0=0\)
b)
2x-1 là bội của x+3
=> 2x-1 chia hết cho x+3
hay [2(x+3)-7] chia hết ho x+ 3
=> 7 chia hết cho x+ 3
x+3 εεƯ(7)={1,-1,7,-7}
x+3=1 x+3=-1 x+3=7 x+3= -7
x = 1-3 x = -1-3 x = 7-3 x = -7-3
x = -2 x = -4 x =4 x = -10
Vậy x= -2, x=-4,x= 4, x= -10
c) \(205-\left[1200-\left(4^2-2.3\right)^3\right]:40\)
\(=205-\left[1200-16-6^3\right]:40\)
\(=205-\left[1200-10^3:40\right]\)
\(=205-1200-1000:40\)
\(=205-200:40\)
\(=205-5\)
\(=200\)
![](https://rs.olm.vn/images/avt/0.png?1311)
= 205 - [(1200 - (16 - 2 . 3)3 ] : 40
= 205 - [1200 - (16 - 6)3 ] : 40
= 205 - [1200 - 103 ] : 40
= 205 - [1200 - 1000 ] : 40
= 205 - 200 : 40
= 205 - 5
= 200
Tick nha bạn
205 - [(1200 - (42 - 2 . 3)3 ] : 40
= 205 - [(1200 - (16 - 2 . 3)3 ] : 40
= 205 - [1200 - (16 - 6)3 ] : 40
= 205 - [1200 - 103 ] : 40
= 205 - [1200 - 1000 ] : 40
= 205 - 200 : 40
= 205 - 5
= 200
![](https://rs.olm.vn/images/avt/0.png?1311)
mk từng làm dạng này rồi chỉ khác 1 chút thôi
C = 1 + 3 + 3^2 +...+3^10 +3^11 chia hết cho 13
=( 1+3+3^2) + ( 3^3 + 3^4 + 3^5) + ....+(3^9 + 3^10 + 3^11)
=(1+3 +9) + 3^3+(1+3+3^2) + ........+3^9 +(1+3+3^2)
=13 + 3^3 . 13 +....+ 3^9 . 13
=13. (1+3^3+....+3^9) chia hết cho 13
=>C chia hết cho 13
cứ theo cách đấy mà làm
![](https://rs.olm.vn/images/avt/0.png?1311)
\(205\left[1200-\left(4^2-2.3\right)^3\right]:40\)
\(=205\left[1200-\left(16-6\right)^3\right]:40\)
\(=205\left[1200-10^3\right]:40\)
\(=205\left[1200-1000\right]:40\)
\(=205.200:40\)
\(=205.5\)
\(=1025\)
Ủng hộ nha
205[1200-(42-2.3)3]:40
=205[1200-103]:40
=205.200:40
=1025
![](https://rs.olm.vn/images/avt/0.png?1311)
205 - [ 1200 - ( 42 - 2 . 3 )3 ] : 40
= 205 - [ 1200 - ( 16 - 2 . 3 )3 ] : 40
= 205 - [ 1200 - ( 16 - 6 )3 ] : 40
= 205 - [ 1200 - 103 ] : 40
= 205 - [ 1200 - 1000 ] : 40
= 205 - 200 : 40
= 205 - 5
= 200
![](https://rs.olm.vn/images/avt/0.png?1311)
X2x—7=15
2x=15+7
2x=22
x=22:2
x=11
4x +5=205
4x=205–5
4x=200
x=200:4
x=50
80/(x+1)=40
==> 80: x+1=40
80:x=40-1
80:x=39
x=80:39
x=80/39
72–(2x—4)=2
2x—4=72-2
2x—4=70
2x=70+4
2x=74
x=74:2
x=37
75-5(x+3)=5
5(x+3)=75–5
5(x+3)=70
x+3=70:5
x+3=14
x=14–3
x=11
7x:7=4
7x=4.7
7x=28
x=28:7
x=4
20:(x—5)=20
x—5=20:20
x—5=1
x=1+5
x=6
9(2x—8)=0
2x=0:9
2x=0
x=0:2
x=0
2080:4x=40
4x=2080:40
4x=52
x=52:4
x=13
![](https://rs.olm.vn/images/avt/0.png?1311)
205 - [ 1200 - ( 42 - 2 . 3)3 ] : 40
= 205 - [ 1200 - 1000 ] : 40
=205 - 200 : 40
= 205 - 5
= 200
Bài làm
205 - [ 120 - ( 42 - 2 . 3 )3 ] : 40
= 205 - [ 120 - ( 14 - 1 . 3 )3 ] : 40
= 205 - [ 120 - ( 14 - 3 )3 ] : 40
= 205 - [ 120 - 113 ] : 40
= 205 - [ 120 - 1331 ] : 40
= 205 - ( -1211 ) : 40
= 205 + 1211 : 40
= 205 + 30,275
= 235,275
# Chúc bạn học tốt #
![](https://rs.olm.vn/images/avt/0.png?1311)
205-[1200-(42-2.3)3]:40
=205-[1200-(16-2.3)3]:40
=205-[1200-(16-6)3]:40
=205-[1200-103]:40
=205-[1200-1000]:40
=205-200:40
=205-50
=155
Nhớ thk nha bạn
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