x+x+x nhân 5= 350 (cần đáp án nhanh)
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Số số hạng của dãy là : \(\left(45-1\right)\div4+1=12\)( số )
Ta có :
\(\left(x+1\right)+\left(x+5\right)+\left(x+9\right)+....+\left(x+45\right)=331,2\)
\(\Leftrightarrow12\times x+\frac{\left(45+1\right)\times12}{2}=331,2\)
\(\Leftrightarrow12\times x+276=331,2\)
\(\Leftrightarrow12\times z=55,2\)
\(\Leftrightarrow x=4,6\)
Vậy \(x=4,6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1:
\(3x\left(12x+4\right)+9x\left(4x+3\right)\)
\(\Leftrightarrow3x\left(12x+4\right)+3x\left[3.\left(4x+3\right)\right]\)
\(\Leftrightarrow3x\left(12x+4\right)+3x\left(12x+6\right)\)
\(\Leftrightarrow3x\left[12x+4+12x+6\right]\)
\(\Leftrightarrow3x.\left(24x+10\right)\)
\(\Leftrightarrow72x^2+30x\)
Câu 2:
\(x\left(5+2x\right)+2x^2\left(x-1\right)\)
\(\Leftrightarrow5x+2x^2+2x^3-2x^2\)
\(\Leftrightarrow2x^3+5x\)
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|x-2,2| =|0,2-x|<=> |x-2,2| -|0,2-x| = 0
|x-2,2|>=0
|0,2-x|>=0
mà |x-2,2|-|0,2-x| =0
hoặc =>x-2,2=0=> x =2
hoặc =>0,2-x=0=> x =0,2
![](https://rs.olm.vn/images/avt/0.png?1311)
x . 15 + x + 15 = 463
x . 15 + x = 463 - 15
x . 15 + x = 448
x . ( 15 + 1 ) = 448
x . 16 = 448
x = 448 : 16
x = 28
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(2x-3\right)\left(x+3\right)\left(5-x\right)\)
\(=\left(2x^2+6x-3x-9\right)\left(5-x\right)\)
\(=10x^2+30x-15x-45-2x^3-6x^2+3x^2+9x\)
\(=-2x^3+7x^2+24x-45\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: -12.(x-5)+7(3-x)=-12x-(-60)+21-7x=-12x-7x+81=-19x+81=5 => -19x=76
=> x=-4
Vậy x=-4
![](https://rs.olm.vn/images/avt/0.png?1311)
20 000 - x * 5 =12485
x*5=20 000 - 12485
x*5=7515
x=7515:5
x=1503
![](https://rs.olm.vn/images/avt/0.png?1311)
x x 10 -x = 1
x x 9 = 1
x =1:9
x =1/9
1/9 là một phần chín nhé
X + X + X x 5 = 350
X x 1 + X x 1 + X x 5 = 350
X x (1 + 1 + 5) = 350
X x 7 = 350
X = 350 : 7
X = 50
chời ơi :$_$