\(a,\dfrac{-13}{5}-\dfrac{-7}{15}.\dfrac{120}{63}+\dfrac{4}{5}\\ =\dfrac{-13}{5}+\dfrac{8}{9}+\dfrac{4}{5}\\ =\dfrac{-77}{45}+\dfrac{4}{5}\\ =\dfrac{-41}{45}\\ b.\left(7\dfrac{5}{9}+2\dfrac{2}{3}\right)-5\dfrac{2}{9}\\ =\left(\dfrac{68}{9}+\dfrac{8}{3}\right)-\dfrac{47}{9}\\ =\dfrac{92}{9}-\dfrac{47}{9}\\ =5\)

2)\(-\dfrac{13}{5}--\dfrac{7}{15}.\dfrac{120}{63}+\dfrac{4}{5}\)
\(=-\dfrac{13}{5}+\dfrac{7.15.8}{15.9.7}+\dfrac{4}{5}\)
\(=-\dfrac{13}{5}+\dfrac{8}{9}+\dfrac{4}{5}\)
\(=\left(-\dfrac{13}{5}+\dfrac{4}{5}\right)+\dfrac{8}{9}\)
\(=-\dfrac{9}{5}+\dfrac{8}{9}\)
\(=\dfrac{-81+40}{45}=-\dfrac{41}{45}\)
3)\(\left(7\dfrac{5}{9}+2\dfrac{2}{3}\right)-5\dfrac{2}{9}\)
\(=\left(7\dfrac{5}{9}-5\dfrac{2}{9}\right)+2\dfrac{2}{3}\)
\(=2\dfrac{1}{3}+2\dfrac{2}{3}\)
\(=5\)

1) 167 + ( -252 ) + 52 + ( -67 )

= 167 + 52 + ( -252 ) + ( - 67 )

= 219 + - ( 252 + 67 )

= 219 + - ( 319 )

= -100

2) ( -215 ) + ( - 115 ) + ( - 80 )

= - ( 215 + 115 ) + ( - 80 )

= - 330 + ( - 80 )

= - ( 330 - 80 )

= - 250

3) 118 + 107 - ( 118 - 93 )

= 118 + ( 107 - 93 ) 

= 118 + 14

= 132

4) 1 + 5 + 9 + ..... + 97 + 101

= ( 101 : 1) - 4 = 96

= 101  x 96

= 9696

5) 38 - 138 + 250 - 350

= - 100 + - 100

= 0

6) - ( - 357 ) + ( - 27 ) + ( - 32 )

= - ( - 357 ) + - ( 27 + 32 )

= - ( - 357 ) + - 59

= - ( 357 + 59 )

= - 416

7) 40 + ( 139 - 172 + 99 ) - ( 139 + 199 - 172 )

= 40 + ( 100 - 100 )

= 40 + 0

= 40

8) ( -1 ) + 2 + ( - 3 ) + 4 + ( - 99 ) + 100

gì nhiều thế

\(99-97+95-93+91-89+...+7-5+3-1\)

\(=\left(99-97\right)+\left(95-93\right)+...\left(7-5\right)+\left(3-1\right)\)

\(=2.25\)

\(=50\)

ta thấy 

\(4000:82=48\)  ( dư 674)

số \(64>47\Rightarrow\)  số bị chia < 4000 là :

\(82.48+47=3983\) 

vì 3983<4000 ( t/m)

=> số chia là 48

123 + [ 54 + ( - 123 ) + 46 ]

= 123 + [ - 69 + 46 ]

= 123 + ( - 23 )

= 100 

TK

Bài làm

123 + [ 54 + ( -123 ) + 46 ]

= 123 + [ 54 - 123 + 46 ]

= 123 - 23

= 100

Bỏ ngoặc rồi tính

a) - ( 213 + 74 ) - ( - 2013 - 26 )= -213 -74 + 2013 + 26 =  1752

b) ( 56 + 83 ) - ( 56 - 17 )= 56 + 83 -56+ 17 = 100

c) - ( 92 - 18 ) + ( 92 - 118 )= -92 + 18 + 92 -118 = -100

a)=-213-74-213+26

=-474

a) ( x - 35 ) - 120 = 0

      x - 35             = 120

      x                     = 120 + 35

      x                     = 155

Vậy x = 155

b) 124 + (118 - x) = 217

                118 - x  = 217 - 124

                 118 - x = 93

                          x = 118 - 93

                          x = 25

Vậy x = 25

c) 156 - (x + 61) = 82

              x + 61  = 156 - 82

              x + 61  = 74

              x          = 74 - 61

              x          = 13

Vậy x = 13

2.

321 - 96 = ( 321 + 4 ) - ( 96 + 4 ) 

              = 325 - 100

              = 225

46 + 29 = ( 46 + 4 ) + ( 29 - 4 )

             = 50 + 25

             = 75

a=0

b=-14

c=1

a. 92 + (− 22) = 70
b. (− 801) + (− 199) = -1000
c. −345 − (− 209) = -136

d. 116 − 128 = -12
e. (− 304) + 195 = -109
f. (− 457) + 457 = 0

 a¹² : a⁸ = a^{12 -8} = a⁴ 

a¹⁰ : a = a^{10- 1} = a⁹  

a⁷ . a⁴ = a⁷⁺⁴  = a¹¹