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Có 3x+4chia hết cho 3x-1
=> 3x-1 chia hết cho 3x-1
=>(3x+4)-(3x-1)chia hết cho 3x-1
=>5 chia hết cho 3x-1
=>3x-1 thuộc ước của 5
=>3x-1 thuộc {1;5;-1;-5}
Ta có bảng
3x-1 1 5 -1 -5
x 2/3 2 0 -4/3
NĐ Loại Chọn Chọn Loại
Vậy x thuộc {2;0}
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=3x-x^2\)
\(=-\left(x^2-2.x.\frac{3}{2}+\left(\frac{3}{2}\right)^2-\frac{9}{4}\right)\)
\(=-\left(\left(x-\frac{3}{2}\right)^2-\frac{9}{4}\right)\)
\(=\frac{9}{4}-\left(x-\frac{3}{2}\right)^2\ge\frac{9}{4}\)
Min A = \(\frac{9}{4}\)khi \(x-\frac{3}{2}=0=>x=\frac{3}{2}\)
\(B=25+2x-x^2\)
\(=-\left(x^2-2x+1-26\right)\)
\(=-\left(\left(x-1\right)^2-26\right)\)
\(=26-\left(x-1\right)^2\ge26\)
Min A = 26 khi \(x-1=0=>x=1\)
\(C=x^2-5x+19\)
\(=x^2-2.x.\frac{5}{2}+\left(\frac{5}{2}\right)^2+\frac{51}{4}\)
\(=\left(x+\frac{5}{2}\right)^2+\frac{51}{4}\ge\frac{51}{4}\)
Min C = \(\frac{51}{4}\)khi \(x+\frac{5}{2}=0=>x=\frac{-5}{2}\)
@@@ nha các bạn . Thanks
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2\text{x}-1}{3}=\dfrac{3\text{x}+1}{4}\)
\(\Leftrightarrow=\dfrac{4\left(2\text{x}-1\right)}{12}=\dfrac{3\left(3\text{x}+1\right)}{12}\)
\(\Leftrightarrow8\text{x}-4=9\text{x}+3\)
\(\Leftrightarrow8\text{x}-9\text{x}=3+4\)
\(\Leftrightarrow-x=7\)
\(\Leftrightarrow x=-7\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(3^x-27.3^5.3^2=0\)
\(3^x-3^3.3^5.3^3=0\)
\(3^x=3^{13}\)
\(x=13\)
b) \(\left(-5+3x\right):4=16\)
\(-5+3x=64\)
\(3x=69\)
\(x=23\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)5-2x=3x+20
5=3x+20+2x
5=5x+20
=>5x+20=5
5x=5-20
5x=-15
x=(-15):5
x=-3
![](https://rs.olm.vn/images/avt/0.png?1311)
(27 + 29) + (86 - 84) + 5
= 56 + 2 + 5
= 63
Chúc bạn học tốt!! ^^
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x+2x+3x+...+100x=2200\)
=>\(x\left(1+2+3+...+100\right)=2200\)
=>\(x.\frac{100.101}{2}=2200\)
=>\(x.5050=2200\)
=>x=2200:5050
=>x=\(\frac{44}{101}\)
\(x+2x+3x+...+100x=220\)
\(\Rightarrow x\left(1+2+3+....+100\right)=2200\)
\(\Rightarrow5050x=2200\)
\(\Rightarrow x=\frac{44}{101}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
H = 1 x 2 + 2 x 3 + 3 x 4 + ... + 2017 x 2018
3H = 1 x 2 x 3 + 2 x 3 x 3 + 3 x 4 x 3 + .. + 2017 x 2018 x 3
3H = 1 x 2 x 3 + 2 x 3 x ( 4 - 1 ) + 3 x 4 x ( 5 - 2 ) + .. + 2017 x 2018 x ( 2019 - 2016 )
3H = 1 x2 x 3 + 2 x3 x4 - 1 x 2 x3 + 3x 4 x5 - 2x 3 x4 +...+ 2017 x 2018 x 2019 - 2016 x 2017 x 2018
3H = 2017 x 2018 x 2019
=> H = 2739315938
2.3x+2+4.3x+1=10.32013
=>4.3x+2+2.3x+1=10.32013
=>4.3x+2+2.3x+1-10.32013=10.32013-10.32013
=>-10.32013+4.3x+2+2.3x+1=0
Mk chỉ giải đc đến đây thui !