\(\left(-x+31\right)-39=69+11\Leftrightarrow-x+31-39=80\)

\(\Leftrightarrow\) \(-x=80+39-31=88\) \(\Leftrightarrow\) \(x=-88\) vậy \(x=-88\)

\(\left(-x+31\right)-39=69+11\)

\(\Leftrightarrow\left(-x+31\right)-39=80\)

\(\Leftrightarrow-x+31=80+39\)

\(\Leftrightarrow-x+31=119\)

\(\Leftrightarrow-x=119-31\)

\(\Leftrightarrow-x=88\Rightarrow x=-88\)

( -x + 31 ) - 39 = 69 + 11

( -x + 31 ) - 39 = 80

( -x + 31 ) = 80 + 39

-x + 31 = 119

-x = 119 - 31

-x = 88

x = -88

b: \(\Leftrightarrow-37+57+x=20\)

hay x=0

(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 :

\((-x+31)-39=-69+11\)

\((-x+31)-39=-58\)

\(-x+31=-58+39\)

\(-x+31=-19\)

\(-x=-19-31\)

\(-x=-50\)

\(=>x=50\)

(-x+31)-39=-69+11

(-x+31)-39=-58

-x+31        =-58+39

-x+31        =-19

-x              =-19-31

-x              =-50

(31-x)-39=11-69

31-x=11-69+39

31-x=-19

x=50

37+| 7-x | =127

|7-x |  = 90

7-x=90 hoặc 7-x=-90

x=-81 hoắc x=97

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

a) (-x + 31) - 39 = -69 + 11

=> - x + 31 - 39 = -58

=> - x = - 58 - 31 + 39

=> - x = - 50

=> x = 50

vậy_

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) \(\left(-69\right)\cdot\left(-31\right)-\left(-15\right)\cdot12\)

\(=69\cdot31+15\cdot12\)

\(=2139+180\)

\(=2319\)

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: \(\left[\left(-4\right)\cdot\left(-9\right)-6\right]\left[\left(-12\right)-\left(-7\right)\right]\)

\(=\left[36-6\right]\left[-12+7\right]\)

\(=30\cdot\left(-5\right)=-150\)

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

giúp nha 

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