5x + 3.(10-x) + x = 45
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\(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+.......+\dfrac{1}{x\cdot\left(x+1\right)}=\dfrac{122}{123}\)
\(\Leftrightarrow1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+......+\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{122}{123}\)
\(\Leftrightarrow1-\dfrac{1}{x+1}=\dfrac{122}{123}\)
\(\Leftrightarrow\dfrac{1}{x+1}=\dfrac{1}{123}\)
\(\Leftrightarrow x=122\)
(-23)+(+31)=8
(-37)+65+(-12)+(-1)=15
tim x
-5<x<5
=> x thuộc {-4;-3;-2;-1;0;1;2;3;4;5}
219-7.(x+1)=10
7.(x+1)=219-10
7.(x+1)=209
x+1=209:7
x+1=27
x =27-1
x =26
(3x-6).3=34
(3x-6).3=81
3x-6 =81:3
3x-6 =27
3x =27+6
3x =33
x =33:3
x =11
a) \(5+3^{x+1}=86\)
\(=>3^{x+1}=86-5\)
\(=>3^{x+1}=81=3^4\)
\(=>x+1=4\) ( cùng cơ số )
\(=>x=4-1\)
\(=>x=3\)
b) \(15:\left(x+2\right)=\left(3^3+3\right):10\)
\(=>15:\left(x+2\right)=\left(27+3\right):10\)
\(=>15:\left(x+2\right)=30:10=3\)
\(=>x+2=15:3\)
\(=>x+2=5\)
\(=>x=5-2\)
\(=>x=3\)
c) \(\left(9x+2\right).4=80\)
\(=>9x+2=80:4\)
\(=>9x+2=20\)
\(=>9x=20-2\)
\(=>9x=18\)
\(=>x=18:9\)
\(=>x=2\)
d) \(\left(245-x\right)+7^2=14\)
\(=>\left(245-x\right)+14=14\)
\(=>245-x=14-14\)
\(=>245-x=0\)
\(=>x=245-0\)
\(=>x=245\)
a, 7x . (x-10 ) = 0
=> \(\hept{\begin{cases}7x=0\\x-10=0\end{cases}}\) => \(\hept{\begin{cases}x=0\\x=10\end{cases}}\)
b,17 . (3x-6).(2x-8) = 0
(3x-6).(2x-8) = 0 : 17
(3x-6).(2x-8) = 0
=>\(\hept{\begin{cases}3x-6=0\\2x-8=0\end{cases}}\)=>\(\hept{\begin{cases}x=2\\x=4\end{cases}}\)
Nhớ nha
\(5\cdot x+10\cdot9=990\)
\(\Rightarrow5\cdot x+90=990\)
\(\Rightarrow5\cdot x=900\)
\(\Rightarrow x=\dfrac{900}{5}\)
\(\Rightarrow x=180\)
_____________
\(1045:\left[215-\left(3\cdot x-24\right)\right]=5\)
\(\Rightarrow215-\left(3\cdot x-24\right)=1045:5\)
\(\Rightarrow215-\left(3\cdot x-24\right)=209\)
\(\Rightarrow3\cdot x-24=215-209\)
\(\Rightarrow3\cdot x-24=6\)
\(\Rightarrow3\cdot x=30\)
\(\Rightarrow x=10\)
`@` `\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.`
\(\frac{2}{5}.\frac{1}{x}+\frac{1}{x}.2+\frac{2}{5}=0,5\)
\(\Rightarrow\frac{2}{5x}+\frac{2}{x}+\frac{2}{5}=\frac{1}{2}\)
\(\Rightarrow2.\left(\frac{1}{5x}+\frac{1}{x}+\frac{1}{5}\right)=\frac{1}{2}\)
\(\Rightarrow\frac{1}{5x}+\frac{5}{5x}+\frac{x}{5x}=\frac{1}{2}:2=\frac{1}{4}\)
\(\Rightarrow\frac{1+5+x}{5x}=\frac{1}{4}\)
\(\Rightarrow4.\left(1+5+x\right)=5x\)
\(\Rightarrow4+20+4x=5x\)
\(\Rightarrow24+4x=5x\)
\(\Rightarrow5x-4x=24\)
\(\Rightarrow x=24\)
Bạn ơi !
đề bài của bạn : (x=+5).12=60 mình nghĩ là nhầm lẫn chỗ x=+5
Nếu đề bài đúng mình nghĩ là(x+5).12=60
<=>x+5=60:12=5
<=>x=5-5=0
KL: Vậy x = 0
a) \(\left(5x+3^4\right).6^8=6^9.3^4\)
\(=>6x+3^4=3^4.6^9:6^8\)
\(=>6x+3^4=3^4.6\)
\(=>6x=6.3^4-3^4\)
\(=>6x=0\)
\(=>x=0:6\)
\(=>x=0\)
a/(5x + 34).68=69.34
(5x + 34) = 69:68.34
5x + 81 = 6.81
5x = 6.81 - 81
5x = 486 - 81
5x = 425
x = 425:5
x = 85
b/92 - 2x = 2.42- 3.4 + 120:15
92 - 2x = 2.16 - 12 + 8
92 - 2x = 32 - 12 + 8
92 - 2x = 28
2x = 92 - 28
2x = 64
x = 64:2
x = 32
c/53.(3x + 2) : 13 = 103: (135:134)
125.(3x + 2) : 13 = 1000:13
125.(3x+2) = 1000:13.13
125.(3x+2) = 1000
3x + 2 = 1000:125
3x + 2 = 8
3x = 8 - 2
3x = 6
x = 6:3
x = 2
Bạn nhớ tick cho mình nhé!
5x + 3(10-x) + x = 45
5x + 3.10 - 3.x + x = 45
5x - 3x + x + 30 = 45
3x = 45-30
3x = 15
x = 15:3
x = 5
Vậy x = 5
x=5 nha
nếu đúng k