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1a) 25 .8 - 12.5 + 272 :17 - 8
= 200 - 60 + 16 - 8
= 140+16-8
= 156 - 8
= 148
b) 125: 25 +14 - 142 : 71
= 5 + 14 - 2
= 19 - 2 = 17
c) 13. 17 - 256: 16 + 14 : 7 - 1
= 221 - 16 + 2 - 1
= 205 + 2 - 1
= 207 - 1 = 206
d) 15 . 24 - 14 . 5 (145 : 5 - 27)
= 360 - 70 (29- 27)
= 360 - 70 . 2
= 360 - 140
= 220
2a) 37 + x = 55
x= 55 - 37
x = 18
b) x- 31 = 24
x = 24 + 31
x = 55
c) 21 (x-11) = 21
x - 11 = 21 : 21
x = 1 +11
x = 12
d ) 9. (x - 29)= 0
x - 29 = 0 :9
x = 29
e) (x - 1954) . 5 = 50
x - 1954 = 50 : 5
x = 1964
f ) 30 . 60 - x = 30
1800 - x = 30
x = 1800 - 30
x = 1770
Viết mỏi tay quá huhuh
![](https://rs.olm.vn/images/avt/0.png?1311)
a) (-37 - 17) . (-9) + 35 . (-9 - 11)
=-54*(-9)+35*(-20)
=486+(-700)
=-214
b) (-25) . (75 - 45) - 75 . ( 45 - 25)
=(-25)*30-75*20
=-750-1500
=-2250
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x-17=\left(-8\right)-17\)
\(\Rightarrow x=-8-17+17\)
\(\Rightarrow x=-8\)
\(25-\left(11+x\right)=x-\left(34-18\right)\)
\(\Rightarrow25-11-x=x-34+18\)
\(\Rightarrow-x-x=-34+18+11-25\)
\(\Rightarrow-2x=-30\)
\(\Rightarrow x=15\)
\(6-\left(17-x\right)=3x-7\)
\(\Rightarrow6-17+x=3x-7\)
\(\Rightarrow x-3x=-7+17-6\)
\(\Rightarrow-2x=4\)
\(\Rightarrow x=-2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x\left(x-6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x-6=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=6\end{matrix}\right.\)
b) \(\left(-7-x\right)\left(-x+5\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}-7-x=0\\-x+5=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=-7\\x=-5\end{matrix}\right.\)
c) \(\left(x+3\right)\left(x-7\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x+3=0\\x-7=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=-3\\x=7\end{matrix}\right.\)
d) \(\left(x-3\right)\left(x^2+12\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-3=0\\x^2+12=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=3\\x^2=-12\text{(vô lý)}\end{matrix}\right.\)
\(\Rightarrow x=3\)
e) \(\left(x+1\right)\left(2-x\right)\ge0\)
\(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x+1\ge0\\2-x\ge0\end{matrix}\right.\\\left[{}\begin{matrix}x+1\le0\\2-x\le0\end{matrix}\right.\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x\ge-1\\x\le2\end{matrix}\right.\\\left[{}\begin{matrix}x\le-1\\x\ge2\end{matrix}\right.\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}-1\le x\le2\\x\in\varnothing\end{matrix}\right.\)
\(\Rightarrow-1\le x\le2\)
f) \(\left(x-3\right)\left(x-5\right)\le0\)
\(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x-3\le0\\x-5\ge0\end{matrix}\right.\\\left[{}\begin{matrix}x-3\ge0\\x-5\le0\end{matrix}\right.\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x\le3\\x\ge5\end{matrix}\right.\\\left[{}\begin{matrix}x\ge3\\x\le5\end{matrix}\right.\end{matrix}\right.\)
\(\Rightarrow3\le x\le5\)
a) =>\(\left[{}\begin{matrix}x=0\\x-6=0\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\x=6\end{matrix}\right.\)
b => \(\left[{}\begin{matrix}-7-x=0\\-x+5=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-7\\x=5\end{matrix}\right.\)
d) => \(\left[{}\begin{matrix}x-3=0\\x^2+12=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3\\x^2=-12\end{matrix}\right.\)(vô lí) => x=3
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,2-x=17-\left(-5\right)\)
\(\Rightarrow2-x=17+5\)
\(\Rightarrow2-x=22\)
\(\Rightarrow x=2-22\)
\(\Rightarrow x=-20\)
Vay...
\(b,11-\left(15+11\right)=x-\left(25-9\right)\)
\(\Rightarrow11-26=x-16\)
\(\Rightarrow-15=x-16\)
\(\Rightarrow-15+16=x\)
\(\Rightarrow x=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x+5=20-\left(12-7\right)\)
\(\Rightarrow x+5=20-5\)
\(\Rightarrow x+5=15\)
\(\Rightarrow x=15-5\)
\(\Rightarrow x=10\)
b) \(15-\left(3+2x\right)=2^2\)
\(\Rightarrow3+2x=15-4\)
\(\Rightarrow3+2x=11\)
\(\Rightarrow2x=11-3\)
\(\Rightarrow2x=8\)
\(\Rightarrow x=\dfrac{8}{2}\)
\(\Rightarrow x=4\)
c) \(-11-\left(19-x\right)=50\)
\(\Rightarrow19-x=-11-50\)
\(\Rightarrow19-x=-61\)
\(\Rightarrow x=61+19\)
\(\Rightarrow x=80\)
d) \(159-\left(25-x\right)=43\)
\(\Rightarrow25-x=159-43\)
\(\Rightarrow25-x=116\)
\(\Rightarrow x=25-116\)
\(\Rightarrow x=-91\)
e) \(\left(79-x\right)-43=-\left(17-52\right)\)
\(\Rightarrow\left(79-x\right)-43=52-17\)
\(\Rightarrow79-x-43=35\)
\(\Rightarrow36-x=35\)
\(\Rightarrow x=1\)
f) \(\left(7+x\right)-\left(21-13\right)=32\)
\(\Rightarrow7+x-8=32\)
\(\Rightarrow x-1=32\)
\(\Rightarrow x=32+1\)
\(\Rightarrow x=33\)
g) \(-x+20=-15+8+13\)
\(\Rightarrow-x+20=6\)
\(\Rightarrow x=20-6\)
\(\Rightarrow x=14\)
h) \(-\left(-x+13-142\right)+18=55\)
\(\Rightarrow x-13+142+18=55\)
\(\Rightarrow x+147=55\)
\(\Rightarrow x=55-147\)
\(\Rightarrow x=-92\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1. THực hiện phép tính :
a) 17 - 25 + 55 - 17
= ( 17 - 17 ) + ( -25 + 55 )
= 0 + 30 = 30
b) 25 - (-75) + 32 - (32 + 75)
= 25 + 75 + 32 - 32 - 75
= 25 + ( 75 - 75 ) + ( 32 - 32 )
= 25 + 0 + 0 = 25
c) (-5).8.(-2).3
= [(-5).(-2)].(8.3)
= 10 . 24 = 240
d) (-15) + (- 122) = - ( 15 + 122 ) = -137
e) /-127/ - 18.(5-6)
= 127 - 18.(-1)
= 127 - ( -18 ) = 127 + 18 = 145
Trả lời
1.Thực hiện phép tính :
a)17-25+55-17
=(17-17)-25+55
=0-25+55
=30
b)25-(-75)+32-(32+75)
=25+75+32-32-75
=25+(75-75)+(32-32)
=25+0+0
=25
c)(-5).8.(-2).3
=[(-5).(-2)].3.8
=10.24
=240
d)(-15)+(-122)
=(-137)
e)|-127|-18.(5-6)
=127-18.(-1)
=127.(-18)
=(-2286)
Bài 2:
a)Ư (-8)={-1;-2;-4;-8}
b)B (-11)={-11;-22;-33;-44;-55}
Bài 3:
a)-13+x=39
=>x=39+13
=>x=52
b)3x-(-17)=14
3x+17 =14
3x =14-17
3x =(-3)
x =(-3):3
x =(-1)
c)|x+9|.2=10
|x+9| =10:2
|x+9| =5
|x| =5-9
|x| =-4
Vậy: x=4 hoặc -4
d)
12=22.3
10=2.5
BCNN (12;10)=22.3.5=60
BC (12;10) = {60;120;180}
Vậy x có thể là 1 trong 3 số trên: 60;120;180.
a) ( x- 55 ) . 17 = 0
x - 55 = 0 : 17
x - 55 = 0
x = 0 + 55
x = 55
Vậy x = 55
b) 25 . ( x - 75 ) = 25
x - 75 = 25 : 25
x - 75 = 1
x = 1 + 75
x = 76
Vậy x = 76
c) ( x - 5 ) ( x - 7 ) = 0
=> x - 5 = 0 hoặc x - 7 = 0
x = 0 + 5 x = 0 + 7
x = 5 x = 7
Vậy \(x\in\left\{5;7\right\}\)
d) ( x -11 ) ( x + 17 ) = 0
=> x - 11 = 0 hoặc x + 17 = 0
x = 0 + 11 x = 0 - 17
x = 11 x = -17
Vậy \(x\in\left\{11;-17\right\}\)
a,( x-55).17=0
x-55=0:17
x-55=0
x=0+55
x=55