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Bài 4:
\(a,\Rightarrow5⋮x\Rightarrow x\inƯ\left(5\right)=\left\{1;5\right\}\\ b,\Rightarrow x-2+7⋮x-2\\ \Rightarrow x-2\inƯ\left(7\right)=\left\{1;7\right\}\\ \Rightarrow x\in\left\{3;9\right\}\\ c,\Rightarrow3\left(x+1\right)+4⋮x+1\\ \Rightarrow x+1\inƯ\left(4\right)=\left\{1;2;4\right\}\\ \Rightarrow x\in\left\{0;1;3\right\}\\ d,\Rightarrow10x+6⋮2x-1\\ \Rightarrow5\left(2x-1\right)+11⋮2x-1\\ \Rightarrow2x-1\inƯ\left(11\right)=\left\{1;11\right\}\\ \Rightarrow x\in\left\{1;6\right\}\\ e,\Rightarrow x\left(x+3\right)+11⋮x+3\\ \Rightarrow x+3\inƯ\left(11\right)=\left\{1;11\right\}\\ \Rightarrow x=8\left(x\in N\right)\\ f,\Rightarrow x\left(x+3\right)+2\left(x+3\right)+5⋮x+3\\ \Rightarrow x+3\inƯ\left(5\right)=\left\{1;5\right\}\\ \Rightarrow x=2\left(x\in N\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
`a, 18(x-16)=-36`
`=>x-16=-36:18`
`=>x-16=-2`
`=>x=-2+16`
`=>x= 14`
`b,(-12-x):(-5)=3`
`=>-12-x=3 . (-5)`
`=>-12-x=-15`
`=>x= -12-(-15)`
`=>x=-12+15`
`=>x= 3`
`c,11-(-53+x)=97`
`=>-53+x=11-97`
`=>-53+x=-86`
`=>x=-86-(-53)`
`=>x=-86+53`
`=>x= -33`
`d,-9.x+(-7).x=-48`
`=> [-9+(-7) ].x=-48`
`=>-16.x=-48`
`=>x=-48:(-16)`
`=>x= 3`
`e,(2x-1)^3=-27`
`=> (2x-1)^3=-3^3`
`=> 2x-1=-3`
`=>2x=-3+1`
`=>2x=-2`
`=>x=-2:2`
`=>x=-1`
bn tách ra nhé!
Bài 5 :
\(a,5x-16=40+x\)
\(\Leftrightarrow5x-x=40+16\)
\(\Leftrightarrow4x=56\)
\(\Leftrightarrow x=14\)
\(b,-41+2x-\left(-24\right)=4x-23-x\)
\(\Leftrightarrow-41+2x+24=4x-23-x\)
\(\Leftrightarrow2x-4x+x=41-24-23\)
\(\Leftrightarrow-x=-6\)
\(\Leftrightarrow x=6\)
\(c,2\left(x-5\right)-\left(x+6\right)=\left(-7\right)^2\)
\(\Leftrightarrow2x-10-x-6=49\)
\(\Leftrightarrow x=65\)
\(d,120-4\left(1-x\right)=106-3x\)
\(\Leftrightarrow120-4+4x=106-3x\)
\(\Leftrightarrow4x+3x=106-120+4\)
\(\Leftrightarrow7x=-10\)
\(\Leftrightarrow x=-\dfrac{10}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(1-1/2)×(1-1/3)×(1-1/4)×....×(1-1/100)
=(2/2-1/2)x(3/3-1/3)x...x(100/100-1/100)
=1/2x2/3x...x99/100
=1/100
![](https://rs.olm.vn/images/avt/0.png?1311)
Giả sử
\(n^2+13n+44⋮49\Rightarrow n^2+13n+44⋮7\)
Ta có
\(n^2+13n+30+14⋮7\Rightarrow n^2+13n+30⋮7\)
\(n^2+13n+30=\left(n+3\right)\left(n+10\right)⋮7\)
\(\Rightarrow n+3⋮7\) hoặc \(n+10⋮7\) Giả sử \(n+10⋮7\)
\(\Rightarrow\left(n+10\right)-\left(n+3\right)=7⋮7\Rightarrow n+3⋮7\)
\(\Rightarrow\left(n+3\right)\left(n+10\right)⋮49\Rightarrow n^2+13n+30⋮49\)
Ta đã giả sử
\(n^2+13n+30+14⋮49\Rightarrow14⋮49\) => vô lý vậy \(n^2+13n+44\) không chia hết cho 49
![](https://rs.olm.vn/images/avt/0.png?1311)
-5/7 . 2/11 + (-5/7) . 9/11 + 5/7
= -5/7 . 2/11 + -5/7 . 9/11 + (-5/7) . (-1)
= (-5/7) . (2/11 + 9/11 -1)
= (-5/7) . 0
=0
ks nha bạn
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Bài làm
Vì | 2x - 1 | = 5
\(\Rightarrow\hept{\begin{cases}2x-1=5\\2x-1=-5\end{cases}\Rightarrow\hept{\begin{cases}2x=6\\2x=-4\end{cases}\Rightarrow\hept{\begin{cases}x=3\\x=-2\end{cases}}}}\)
Vậy x = 3 hoặc x = -2.
# Học tốt #
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