Bài 8: Quy tắc dấu ngoặc

Bài 1:

1: \(=8-9+10-14+12=9-2=7\)

2: \(=-14-13+9-5=-18-5=-23\)

3: \(=8-18-11=-10-11=-21\)

4: \(=-12+14-17-3=-32+14=-18\)

5: \(=17-15-2=0\)

6: \(=-4-4+8-4=-4\)

Bài 8:

1: \(=-5-9+\left(-18\right)+3=-14-15=-29\)

2: \(=-11+15-13-9-5\)

=4-13-9-5

=-9-9-5

=-18-5=-23

3: \(=-4+8-15-10=4-25=-21\)

4: \(=4+12-5+19=16-5+19=30\)

5: \(=-7+12-9+10=22-16=6\)

6: \(=-28+30-4=2-4=-2\)

7: \(=16+3-5-7+12=28+3-12=16+3=19\)

8: \(=13-\left(-1\right)+\left(-5\right)=8+1=9\)

(x - 12)-15=(20-7)-18

x-12-15=20-7-18

x=20-7-18+12+15

x=22

<=> x - 27 = 13 - 18

x = 13 + 27 - 18 

=> x = 22

\(12+23+\left(-20\right)+\left(-153\right)+8\)
\(=\left(12+8\right)+\left(-20\right)+\left[23+\left(-153\right)\right]\)
\(=20+\left(-20\right)-130\)
\(=0-130\)
\(=-130\)

-130

=>3(x+4)=105

=>x+4=35

=>x=31

128-3(x+4)=23

       3(x+4)=128-23

       3(x+4)=105

         (x+4)=105:3

         (x+4)=35

          x     = 35-4

          x     = 31

128 - 3(x+4) = 23

=>3(x+4) = 128-23

=>3(x+4) = 105

=> x+4 = 105:3

=>x+4 = 35

=> x = 35-4

=> x= 31

Vậy x = 31

Chọn C

x,y khác dấu

\(b,35-\left\{12-\left[-14+\left(-2\right)\right]\right\}\\ =35-\left\{12-\left(-16\right)\right\}\\ =35-28\\ =7\)

\(35-\left\{12-\left[-14+\left(-2\right)\right]\right\}\)
\(=35-\left(12+14+2\right)\)
\(=35-28=7\)

35−{12−[−14+(−2)]}=35−{12−(−16)}=35−28=7

ko thấy j hết trơn

(28−365)−(26+365)

=28+(-365)+(-26)+(-365)

=-337+(-26)+(-365)

=-363+(-365)

=-728

(28−365)−(26+365)

=28+(-365)+(-26)+(-365)

=-337+(-26)+(-365)

=-363+(-365)

=-728

A + B = (a + b - 5) + (-b - c + 1) = a + b - 5 - b - c + 1 = a + (b - b) - c + (-5 + 1)

= a - c - 4.

C - D = (b - c - 4) - (b - a) = b - c - 4 - b + a = (b - b) - c + a - 4

= a - c - 4.

Vậy A + B = C - D.