(- x + 31 ) - 39 = 69 +11
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Leftrightarrow\) \(-x=-58+39-31=-50\) \(\Leftrightarrow\) \(x=50\) vậy \(x=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(3965-2378)-(437-1378)-528
=3965-2378-437-1378-528
=(3965-(437+528))-(2378-1378)
=3000-1000
=2000
Bài 1 :
\((3965-2378)-(437-1378)-528\)
\(=3965-2378-437+1378-528\)
\(=3965-(2378-1378)-(437+528)\)
\(=3965-1000-965\)
\(=(3965-965)-1000\)
\(=3000-1000\)
\(=2000\)
Bài 2 :
\((-x+31)-39=-69+11\)
\((-x+31)-39=-58\)
\(-x+31=-58+39\)
\(-x+31=-19\)
\(-x=-19-31\)
\(-x=-50\)
\(=>x=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
37+| 7-x | =127
|7-x | = 90
7-x=90 hoặc 7-x=-90
x=-81 hoắc x=97
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) (-x+31) -39= -69+11
(-x+31) -39= -58
-x+31=-58+39
-x+31=-19
-x=-19-31
-x=-50
x=50
b)-129-(35-x) =55
35-x=-129-55
35-x=-184
x=35-(-184)
x=219
c) (-37)-l 7-yl =-127
l 7-yl =(-37)-(-127)
l 7-yl =90
=>7-y=90 hoặc 7-y=-90
y=7-90 y=7-(-90)
y=-83 y=97
d) (2y-5)2 =9
(2y-5)2 =32
=>2y-5=3
2y=3+5
2y=8
y=8:2
y=4
e)(1-3x)3= -8
(1-3x)3= (-2)3
1-3x=-2
3x=1-(-2)
3x=3
x=3:3
x=1
**** nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\left(-11\right)\cdot\left(-28\right)+\left(-9\right)\cdot3\)
\(=11\cdot28-9\cdot3\)
\(=\left(10+1\right)\cdot28-27\)
\(=28\cdot10+28-27\)
\(=280+1\)
\(=281\)
b) \(\left(-69\right)\cdot\left(-31\right)-\left(-15\right)\cdot12\)
\(=69\cdot31+15\cdot12\)
\(=2139+180\)
\(=2319\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(\left(-11\right)\cdot\left(-28\right)+\left(-9\right)\cdot13\)
\(=308-117\)
=191
b: \(\left(-69\right)\cdot\left(-31\right)-\left(-15\right)\cdot12\)
\(=2139-\left(-180\right)\)
=2139+180
=2319
c: \(\left[16-\left(-5\right)\right]\cdot\left(-7\right)\)
\(=\left(16+5\right)\cdot\left(-7\right)\)
\(=-7\cdot21=-147\)
d: \(\left[\left(-4\right)\cdot\left(-9\right)-6\right]\left[\left(-12\right)-\left(-7\right)\right]\)
\(=\left[36-6\right]\left[-12+7\right]\)
\(=30\cdot\left(-5\right)=-150\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1. a) (a - b) - (b + c) + (c - a) - (a - b - c) = -(a + b + c)
Ta có VT = (a - b) - (b + c) + (c - a) - (a - b - c)
= a - b - b - c + c - a - a + b + c
= -a - b - c
= -(a + b + c) = VP
b) P = a * (b - a) - b * (a - c) - bc
P = ab - a^2 - ab + bc - bc
P = -a^2
\(\left(-x+31\right)-39=69+11\Leftrightarrow-x+31-39=80\)
\(\Leftrightarrow\) \(-x=80+39-31=88\) \(\Leftrightarrow\) \(x=-88\) vậy \(x=-88\)
\(\left(-x+31\right)-39=69+11\)
\(\Leftrightarrow\left(-x+31\right)-39=80\)
\(\Leftrightarrow-x+31=80+39\)
\(\Leftrightarrow-x+31=119\)
\(\Leftrightarrow-x=119-31\)
\(\Leftrightarrow-x=88\Rightarrow x=-88\)