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a) -105 - 5.x = (-5)^2
=>-105 - 5.x = 25
=> 5.x = -105 - 25
=> 5.x = -130
=> x = -130: 5
=> x = -26
c) 400 -4.|5-x| = (-6)^2
=>400- 4.|5-x| = 36
=> 4.|5-x| = 400-36
=> 4.|5-x| = 364
=> |5-x| = 364:4
=> |5-x| = 91
=> \(\left[\begin{matrix}5-x=91\\5-x=-91\end{matrix}\right.\)
=> \(\left[\begin{matrix}x=5-91\\x=5-\left(-91\right)\end{matrix}\right.\)
=> \(\left[\begin{matrix}x=-86\\x=96\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 5 nữa bạn cố gắng làm giúp mik nha ko thì mình 0 điểm á, nha iu nhìu lém
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3:
\(=\dfrac{1}{7}\cdot\dfrac{3}{5}\cdot\dfrac{5}{6}\cdot\dfrac{5}{8}=\dfrac{1}{7}\cdot\dfrac{1}{2}\cdot\dfrac{5}{8}=\dfrac{5}{112}\)
4:
=>2/3:x=-2-1/3=-7/3
=>x=-2/3:7/3=-2/7
5:
AC=CB=12/2=6cm
IB=6/2=3cm
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1a/ \(\left(15-x\right)+\left(x-12\right)=7-\left(-5+x\right)\)
=> \(\left(15-x\right)+\left(x-12\right)+\left(-5+x\right)=7\)
=> \(15-x+x-12-5+x=7\)
=> \(\left(15-12-5\right)-\left(x+x+x\right)=7\)
=> \(\left(15-12-5\right)-7=3x\)
=> \(3x=-2-7\)
=> \(3x=-9\)
=> \(x=\frac{-9}{3}=-3\)
b/ \(x-\left\{57-\left[42+\left(-23-x\right)\right]\right\}=13-\left\{47+\left[25-\left(32-x\right)\right]\right\}\)
=> \(x-57-42-23-x=13-47+25-32+x\)
=> \(x-x+x=13-47+25-32+57+42+23\)
=> \(x=\left(13+23\right)-\left(47+57\right)+\left(25+57\right)-\left(32+42\right)\)
=> \(x=36-104+82-74\)
=> \(x=-60\)
d/ \(\left(x-3\right)\left(2y+1\right)=7\)
Vì 7 là số nguyên tố nên ta có 2 trường hợp:
TH1: \(\hept{\begin{cases}x-3=1\\2y+1=7\end{cases}}\)=> \(\hept{\begin{cases}x=4\\y=3\end{cases}}\).
TH2: \(\hept{\begin{cases}x-3=7\\2y+1=1\end{cases}}\)=> \(\hept{\begin{cases}x=10\\y=0\end{cases}}\).
Các cặp (x, y) thoả mãn điều kiện: \(\left(4;3\right),\left(10;0\right)\).
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
a)
\(A=\dfrac{-5}{6}\cdot\dfrac{3}{10}\\ =\dfrac{\left(-5\right)\cdot3}{6\cdot10}\\ =\dfrac{-1}{4}\)
b)
\(B=\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{12}\\ =\dfrac{4}{12}-\dfrac{3}{12}+\dfrac{1}{12}\\ =\dfrac{4-3+1}{12}\\ =\dfrac{1}{6}\)
Bài 2:
\(A=\left(\dfrac{-1}{5}\right)\cdot\dfrac{15}{4}+\left|\dfrac{4}{5}-\dfrac{14}{5}\right|:\dfrac{8}{3}\\ =\left(\dfrac{-1}{5}\right)\cdot\dfrac{15}{4}+\left|\dfrac{-10}{5}\right|\cdot\dfrac{3}{8}\\ =\left(\dfrac{-1}{5}\right)\cdot\dfrac{15}{4}+2\cdot\dfrac{3}{8}\\ =\dfrac{-3}{4}+\dfrac{3}{4}\\ =0\)
\(B=\left(\dfrac{-1}{2}\right)^2:1\dfrac{3}{8}+25\%\cdot\dfrac{3}{11}\\ =\left(\dfrac{-1}{2}\right)^2:\dfrac{11}{8}+\dfrac{3}{4}\cdot\dfrac{3}{11}\\ =\dfrac{1}{4}\cdot\dfrac{8}{11}+\dfrac{3}{4}\cdot\dfrac{3}{11}\\ =\dfrac{8}{44}+\dfrac{9}{44}\\ =\dfrac{17}{44}\)
\(C=\dfrac{-8}{5}+0,6+\left|\dfrac{-1}{2}\right|+\dfrac{1}{2}\\ =\dfrac{-8}{5}+\dfrac{3}{5}+\dfrac{1}{2}+\dfrac{1}{2}\\ =\left(\dfrac{-8}{5}+\dfrac{3}{8}\right)+\left(\dfrac{1}{2}+\dfrac{1}{2}\right)\\ =\left(-1\right)+1\\ =0\)
\(D=\dfrac{-5}{9}\cdot\dfrac{2}{13}+\dfrac{-5}{9}:\dfrac{13}{11}+1\dfrac{5}{9}\\ =\dfrac{-5}{9}\cdot\dfrac{2}{13}+\dfrac{-5}{9}\cdot\dfrac{11}{13}+\dfrac{14}{9}\\ =\dfrac{-5}{9}\cdot\left(\dfrac{2}{13}+\dfrac{11}{13}\right)+\dfrac{14}{9}\\ =\dfrac{-5}{9}\cdot1+\dfrac{14}{9}\\ =\dfrac{-5}{9}+\dfrac{14}{9}\\ =1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2 : Tính
1/ (-15)-/-10/+/-9/-/-5/
=-15-10+9-5
=-21
2/14-(-13)-(-21)+(-32)
=14+13+21-32
=16
3/(-12)-(-17)-(-21)+(-32)
= -12+17+21-32
=-6
4/-/-14/ + /-10/-(-12)+(-8)
=-14+10+12-8
=0
5/-(-11)+(-15)+(+13)-21
=11-15+13-21
=-12
![](https://rs.olm.vn/images/avt/0.png?1311)
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\(1a.8\left(x-7\right)-6\left(x-2\right)=\left|-8\right|.\left(-5\right)\\ \Leftrightarrow8x-56-6x+12=8.\left(-5\right)\\ \Leftrightarrow8x-6x-56+12=40\\\Leftrightarrow 2x=56-12-40\\ \Leftrightarrow2x=4\\ \Leftrightarrow x=2\)
\(b.-7\left(x-5\right)+2\left(7x-14\right)=28\\ \Leftrightarrow-21x+35+14x-28=28\\ \Leftrightarrow-21x+14x=-35+28+28\\ \Leftrightarrow-7x=21\\ \Leftrightarrow x=-3\)
\(c.2x+12=3\left(x-7\right)\\ \Leftrightarrow2x+12=3x-21\\\Leftrightarrow 2x-3x=-12-21\\ \Leftrightarrow-x=-33\\ \Leftrightarrow x=33\)
a) x =5 -13 -8 = -8-8 = -16
b) /x+1/ = 3 -1 =2 => x+1 =2 => x =2-1 =1
hoặc x +1 =-2 => x =-3
Vây x =1 ; -3
c) /x/ = 12 -8
/x/ =4 => x =4 hoặc x =-4