1500:[(30.x+40):x]=30
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\(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+.......+\dfrac{1}{x\cdot\left(x+1\right)}=\dfrac{122}{123}\)
\(\Leftrightarrow1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+......+\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{122}{123}\)
\(\Leftrightarrow1-\dfrac{1}{x+1}=\dfrac{122}{123}\)
\(\Leftrightarrow\dfrac{1}{x+1}=\dfrac{1}{123}\)
\(\Leftrightarrow x=122\)
12000 - ( 1500.2 + 1800.3 + 1800.2 : 3 )
= 12000 - ( 1500.2 + 1800.3 + 3600 : 3 )
= 12000 - ( 3000 + 1800.3 + 3600 : 3 )
= 12000 - ( 3000 + 5400 + 3600 : 3)
= 12000 - ( 8400 + 3600 : 3 )
= 12000 - ( 8400 + 1200 )
= 12000 - 9600
= 2400
\(\left(x-4\right)^9=49.\left(x-4\right)^7\\ =>\left(x-4\right)^9:\left(x-4\right)^7=49\\ =>\left(x-4\right)^2=49\\ =>\left[{}\begin{matrix}x-4=7\\x-4=-7\end{matrix}\right.\\ =>\left[{}\begin{matrix}x=11\\x=-3\end{matrix}\right.\)
(x - 4)9 = 49 . (x - 4)7
(x - 4)9 : (x - 4)7 = 49
(x - 4)2 = 72 = (-7)2
TH1 : TH2 :
(x - 4)2 = 72 (x - 4)2 = (-7)2
x - 4 = 7 x - 4 = -7
x = 7 + 4 x = -7 + 4
x = 11 x = -3
Vậy x = 11 Vậy x = -3
* \(20+65.4=\left(x+75\right):5+30\)
\(\Leftrightarrow20+260-30=\frac{x}{5}+\frac{75}{5}\)
\(\Leftrightarrow20+260-30-\frac{75}{5}=\frac{x}{5}\)
\(\Leftrightarrow235=\frac{x}{5}\Rightarrow x=235.5=1175\)
* \(2248:\left[119-\left(x-6\right)\right]=24\)
\(\Leftrightarrow2248:\left(119-x+6\right)=24\)
\(\Leftrightarrow2248:\left(125-x\right)=24\)
A mình lỡ tay, để mình tính tiếp nhá!
\(\Leftrightarrow125-x=2248:24\Leftrightarrow125-x=\frac{281}{3}\Rightarrow-x=\frac{94}{3}\Rightarrow x=-\frac{94}{3}\)(bài này mình thấy sai sai sao á, nếu mình làm sai thì thông cảm cho mình nhé!
* \(\left(x+70\right):14-40=\left(32.15\right):2\)
\(\Leftrightarrow\left(x+70\right):14=480:2+40\)
\(\Leftrightarrow\frac{x}{14}+5=280\Leftrightarrow\frac{x}{14}=275\Rightarrow x=3850\)
* \(x-4867=\left(175.2050.70\right):25+23\)
\(\Leftrightarrow x-4867-23=\left(175:25\right).\left(2050:25\right).\left(70:25\right)\)
\(\Leftrightarrow x-4890=7.82.\frac{14}{5}\)
\(\Leftrightarrow x-4890=\frac{8036}{5}\Rightarrow x=\frac{8036}{5}+4890=\frac{32486}{5}\)(bài này mình thấy hình như cũng có cái gì đó sai sai luôn hihi!)
\(5\cdot x+10\cdot9=990\)
\(\Rightarrow5\cdot x+90=990\)
\(\Rightarrow5\cdot x=900\)
\(\Rightarrow x=\dfrac{900}{5}\)
\(\Rightarrow x=180\)
_____________
\(1045:\left[215-\left(3\cdot x-24\right)\right]=5\)
\(\Rightarrow215-\left(3\cdot x-24\right)=1045:5\)
\(\Rightarrow215-\left(3\cdot x-24\right)=209\)
\(\Rightarrow3\cdot x-24=215-209\)
\(\Rightarrow3\cdot x-24=6\)
\(\Rightarrow3\cdot x=30\)
\(\Rightarrow x=10\)
`@` `\text {Ans}`
`\downarrow`
`5.x + 10.9 = 990`
`\Rightarrow 5x + 90 = 990`
`\Rightarrow 5x = 990 - 90`
`\Rightarrow 5x = 900`
`\Rightarrow x = 900 \div 5`
`\Rightarrow x = 180`
Vậy, `x = 180`
\(1045 \div [ 215 - (3 . x - 24 ) ] = 5\)
`\Rightarrow 1045 \div (215 - 3x + 24) = 5`
`\Rightarrow 191 + 3x = 1045 \div 5`
`\Rightarrow 191 + 3x = 209`
`\Rightarrow 3x = 209 - 191`
`\Rightarrow 3x =18`
`\Rightarrow x = 18 \div 3`
`\Rightarrow x = 6`
Vậy, `x = 6.`
6+[x.(2+5)]=13
6+(x+7)=13
x+7=13-6
x+7=7
x=7-7
x=0
có khi nào bạn lầm đề ko? x=1 chứ nhỉ
mà 6+ thì phải là 7+
\(\frac{1}{2}.x^2+x=0\)
\(\Leftrightarrow x.\left(\frac{1}{2}x+1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\\frac{1}{2}x+1=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\\frac{1}{2}x=-1\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\x=-2\end{cases}}\)
( x + 70 ) : 14 - 40 = (32 . 15 ) : 2
( x + 70 ) : 14 - 40 = 240
( x + 70 ) : 14 = 240 + 40 = 280
x + 70 = 280 x 14 = 3920
x = 3920 - 70
x = 3850
Vậy x = 3850.
(x+70):14-40=(32.15):2
(x+70):14-40=480;2
(x+70):14-40=240
(x+70);14=240+40
(x+70):14=280
(x+70)=280.14
(x+70)=3360
x=3360-70
x=3290
\(1500:\left[\left(30x+40\right):x\right]=30\)
\(\left[\left(30x+40\right):x\right]=1500:30\)
\(\left[\left(30x+40\right):x\right]=50\)
\(30x:x+40:x=50\)
\(30+40:x=50\Leftrightarrow40:x=50-30\)
\(40:x=20\Leftrightarrow x=40:20\Leftrightarrow x=2\)
1500 : [(30.x+40):x] = 30
\(\left(30.x+40\right):x=50\)
=> 30.x + 40 = 50.x
=> 30.x - 50.x = -40
-20x = -40
x = 2