A=100+(98-97)+(96-95)+(94-93)+…+(2-1)

=100+1+1+1+…+1

Từ 2 đến 98 có: (98-2):2+1=49(số)

=>A=100+1.49

=100+49

=149

Vậy A149

B=1+2-3-4+5+6-7-8+9+10-11-12+…-299-300+301+302

=1+(2-3-4+5)+(6-7-8+9)+(10-11-12+13)+…+(298-299-300+301)+302

=1+302

=303

Vậy B=303

giờ này vẫn đăng toán à bạn

Từ 2 đến 100 ( các số chẵn ) có :

( 100 - 2 ) : 2 + 1 = 50

Từ 1 đến 97 ( các số lẻ ) có :

( 97 - 1 ) : 2 + 1 = 49

A = 100 + 98 + 96 + ...... + 2 - 97 - 95 - 93 - ....... - 1

A = ( 100 + 98 + ....... + 2 ) - ( 97 + 95 + 93 + ...... + 1 )

A = [ ( 100 + 2 ) x 50 : 2 ] - [ ( 97 + 1 ) x 49 : 2 ]

A = 2550 - 2401

1+(-2)+3+(-4)+5+(-6)+7+(-8)+9+(-10)+11+(-12)

=(1+3+5+7+9+11)+[(-2)+(-4)+(-6)+(-8)+(-10)+(-12)]

= 36+-42

=-6

(-1)+2+(-3)+4+(-5)+6+(-7)+8+(-9)+10+(-11)+12

=[(-1)+(-3)+(-5)+(-7)+(-9)+(-11)]+(2+4+6+8+10+12)

=(-36)+42

=6

làm đúng có tick các bạn ơi

thằng nì làm kiểu zì mà khó hỉu thí

1-2-3-4-...-91-92-93-94-95-96-97-98-99=1-(2+3+4+5+..+97+98+99)

                                                       =1-[(2+99).(99-2+1):2]

                                                       =1-(101*98:2)

                                                        =1-4949

                                                         =-4948

ra là 4948

1: =72/90+65/90=137/90

2: =24/56-77/56=-53/56

3: =-7/10+4/5=1/10

4: =15/100-4/100=11/100

5: =4/6-5/6=-1/6

6: =10/40-15/40-76/40=-81/40

7: =-9/10+7/18

=-81/90+35/90=-46/90=-23/45

8: =27/90-55/90=-28/90=-14/45

9: =36/60-50/60-35/60=-49/60

10: =-4/9+5/6-3/8

=-32/72+60/72-27/72

=1/72

\(1,\dfrac{4}{5}+\dfrac{13}{18}=\dfrac{72}{90}+\dfrac{65}{90}=\dfrac{137}{90}\)

\(2,\dfrac{3}{7}-\dfrac{11}{8}=\dfrac{24}{56}-\dfrac{77}{56}=\dfrac{-53}{56}\)

\(3,-\dfrac{7}{10}-\left(-\dfrac{4}{5}\right)=-\dfrac{7}{10}-\left(-\dfrac{8}{10}\right)=\dfrac{1}{10}\)

\(4,\dfrac{3}{20}-\dfrac{1}{25}=\dfrac{75}{500}-\dfrac{20}{500}=\dfrac{55}{500}=\dfrac{11}{100}\)

\(5,\dfrac{2}{3}-\dfrac{5}{6}=\dfrac{12}{18}-\dfrac{15}{18}=-\dfrac{3}{18}=-\dfrac{1}{6}\)

\(6,\dfrac{1}{4}+\left(-\dfrac{3}{8}\right)-\dfrac{19}{10}=\dfrac{8}{32}+\left(-\dfrac{12}{32}\right)-\dfrac{19}{10}=-\dfrac{4}{32}-\dfrac{19}{10}\)

\(=-\dfrac{1}{8}-\dfrac{19}{10}=-\dfrac{10}{80}-\dfrac{152}{80}=-\dfrac{162}{80}=-\dfrac{81}{40}\)

\(7,-\dfrac{9}{10}-\left(-\dfrac{7}{18}\right)=-\dfrac{162}{180}-\left(-\dfrac{70}{180}\right)=-\dfrac{92}{180}=-\dfrac{23}{45}\)

\(8,\dfrac{3}{10}-\dfrac{11}{18}=\dfrac{54}{180}-\dfrac{110}{180}=-\dfrac{56}{180}=-\dfrac{14}{45}\)

\(9,\dfrac{3}{5}-\dfrac{5}{6}+\left(-\dfrac{7}{12}\right)=\dfrac{18}{30}-\dfrac{25}{30}+\left(-\dfrac{7}{12}\right)=-\dfrac{7}{30}+\left(-\dfrac{7}{12}\right)\)

\(=-\dfrac{84}{360}+\left(-\dfrac{210}{360}\right)=-\dfrac{294}{360}=-\dfrac{49}{60}\)

\(10,-\dfrac{4}{9}-\dfrac{-5}{6}-\dfrac{3}{8}=-\dfrac{24}{54}-\dfrac{-45}{54}-\dfrac{3}{8}\)

\(=\dfrac{21}{54}-\dfrac{3}{8}=\dfrac{7}{18}-\dfrac{3}{8}=\dfrac{56}{144}-\dfrac{54}{144}=\dfrac{2}{144}=\dfrac{1}{72}\)

`@mt`

1+2+3+4+5+6+7+8+9+10+11+12+13-1-2-3-4-5-6-7-8-9-10-11-12

=(1-1)+(2-2)+(3-3)+(4-4)+(5-5)+(6-6)+(7-7)+(8-8)+(9-9)+(10-10)+(11-11)+(12-12)+13

=  0  +  0  +  0  +  0  +   0  +  0  +  0  +  0  +  0  + 0  + 0   +  0  +  13

=                                 13

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 - 1 - 2 - 3 - 4 - 5 - 6 - 7- 8 - 9 - 10 

= (1+12) + (2+11) + (3+10) + ( 4+9) + (5+8) + (6+7) + 13 -  (1+11) - ( 2+10) - ( 3+9) - (4+8) - (5+7) + 6 + 12

= 13 * 7 - 12 * 6 + 6

= 13

Ai k mk mk k lại

= 13 nhé hihi nha

1-2-3-4+5-6-7-8+9-10-11-12+...........+97-98-99-100

=(1-2-3-4)+(5-6-7-8)+(9-10-11-12)+.............+(97-98-99-100)

=-8+(-16)+(-24)+..................+(-200)

=-8.(1+2+3+......+25)

=-8.[(25-1):1+1.26:2]

=-8.325

=-2600

-2600

Mình đồng ý với câu trả lời của Việt Anh .

1-2-3-4+5-6-7-8+9-10-11-12+...+97-98-99-100

=(1-2-3-4)+(5-6-7-8)+(9-10-11-12)+...+(97-98-99-100)

=-8+(-16)+(-24)+...+(-200)

=[1.(-8)]+[2.(-8)]+[3.(-8)]+...+[25.(-8)]

=-8.25.26/2

=-8.(1+2+3+...+25)

=-8.325

=-2600