a) \(42+37+135+58+63=\left(42+58\right)+\left(37+63\right)+135=100+100+135=335\)

b) \(25.17.8.4.125=\left(25.4\right).\left(8.125\right).17=100.1000.17=1700000\)

c) \(43.27+93.43+57.61+59.57=43.\left(27+93\right)+57.\left(61+57\right)=43.120+57.120\)

\(=120.\left(43+57\right)=120.100=12000\)

d) \(64.6+81.4+17.6=6.\left(64+17\right)+81.4=6.81+81.4=81.\left(6+4\right)=81.10=810\)

e) \(1+11+21+31+...+991=\left(991+1\right).\left[\left(991-1\right)\div10+1\right]\div2\)

\(=992.\left[990\div10+1\right]\div2=496.\left[99+1\right]=496.100=49600\)

a) 42 + 37 +135+58+63

  =(42+58) + (37=63)+135

  = 100 + 100 + 135

  = 335

b) 25.17.8.4.125

  =(25.4).(8.125).17

  =100.1000.7

  =1700000

c) 43.27 + 93.43 + 57.61 +59.57

  =43.(27 + 93)+57.(61 +59)

  =43.120 + 57.120

  =120.(43+57)

  =120.100

  =12000

d)64.6 + 81.4 +17.6

  =(64 + 17).6 +81.4

  =81.6 + 81.4

  =81.(4+6)

  =81.10

  =810

e)1+11+21+...........+991

    số số hạng của dãy trên là:

       (991-1):10 + 1=100(số hạng)

    tổng dãy số trên là:

       (991+1).100:2=49600

     vậy dãy trên có tổng là 49600

Lời giải:

a. $=-(37+63)+[25+(-25)]+(-9)=-100+0+(-9)=-(100+9)=-109$

b. $=[1+(-3)]+[5+(-7)]+....+[21+(-23)]$

$=\underbrace{(-2)+(-2)+....+(-2)}_{6}=(-2).6=-12$

c. $=-(280+20)+[-(79+21)]=-300+(-100)=-(300+100)=-400$

d. $=[-(27+43)]+[-(208+102)]=-70+(-310)=-(70+310)=-380$

e. $=(38+120)-(12+46)=158-58=100$

f. $=9+15+11+24=(9+11)+(15+24)=20+39=59$

e. = - 1080 + 120 

= -960 

f. (-41) x 59 + ( -41).2 + 59 x 41 - 59 x 2

= 2 x ( -41 - 59 ) 

= 2 x ( -100)

 = -200

g, ( 135 - 35 ) . ( -37 ) + 37 . ( -42 - 58 )

= 100 : ( -37 ) + 37 . -100

= 100 : ( -37 ) + ( 37 . -10 ) . -100

= 100 : ( -37 ) + ( -37 ) . -100

= ( -37 ) . ( 100 + -100 )

= ( -37 ) . 0

= 0

Sai hết rồi ---

a) (-37)+14+26+37 = ( -37 + 37) + ( 14 + 26) = 40
b) (-24)+6+10+24 = ( - 24 + 24) + ( 6 + 10) = 16
c) 15+23+9-25)+(-33) = (15 - 25) + ( 23 - 33) + 9

= - 10 - 10 + 9

= - 11
d) 60+33+(-50)+(-33) = ( 60 -50) + ( 33 - 33)

= 10
e) (-16)+(-209)+(-14)+209 = ( - 16 - 14) + ( - 209 + 209)

= - 30
g) (-12)+(-13)+36+(-11)= ( - 11 -12 - 13 ) + 36

= - 36 + 36 = 0
h) -16+24+16-34 = ( - 16 + 16)+(24 - 34) = - 10
r) 25+37-48-25-37 = (25 - 25)+(37 - 37) - 48 = - 48
u) 2575+37-2576-29 = ( 2575 - 2576) + ( 37 - 29)

= - 1 + 8 = 7
i) 34+35+36+37-14-15-16-17 = ( 34 - 14 )+(35 - 15)+(36-16)+ (37 - 17)

= 80
2 . Bỏ ngoặc rồi tính
a)-7264+(1543+7264) = - 7264 + 1543 + 7264

= 1543
b) (144-97)-144 = 144 - 97 - 144 = - 97
c) (-145)-(18-145) = - 145 - 18 + 145 = - 18
d) 11+(-11+27) = 11 - 11 + 27 = 27
e) (27+514)-(486-73) = 27 + 514 - 486 + 73

= 128
g) (36+79)+(145-79-66) = 36 + 79 + 145 - 79 - 66

= 115
h) 10-[12-(-9-1) = 10 - ( 12 + 9 + 1)

= 10 - 22

= - 12
r) (-28-29+43)-(43+38) = - 28 - 29 + 43 - 43 - 38

= - 95
u ) 271 - [(-43)+271-(-17)] = 271 + 43 - 271 - 17 = 26
i ) -144-[29-(+144)-(+144) = - 144 - 29 - 144 + 144 = -173

Nhiều quá bạn

tự làm

Các bạn nhớ ghi cách làm ra nhé!

8: =>2x=210

hay x=105

a) 52 – 42 + 37 – 28 + 38 + 63 = (52 – 42) + (37 + 63) + (38 – 28) = 10 + 100 + 10 =  120

b) 130 + 35.19 – 9.70 – 30

= (35.19 – 9.70) + (130 – 30) = (35.19 – 9.35.2) + 100 = 35.(19 – 18) + 100 = 35 + 100 = 135

c) (11 + 13 + 15 + … + 19).(6.8 – 48) = (11+13+15+…+19).0 = 0

d) (72 – 8.9):(20+22+24 – 19 +21+23) = 0:(20+22+24 – 19 +21+23) = 0