a.4/20 +16/42+6/15+3/5+2/21_10/21+3/20.

b.6/21_-12/44+10/14_1/-4_18/33.

c. -7/11.8/13+ -7/13.5/11

a. 4/20+16/42+6/15+3/5+2/21_10/21+3/20.             b.6/21_-12/44 +10/14_1/-4_18/33.            c.-7/11.8/13+-7/13.5/11

bài 1:tính số hạng có trong các tổng sau:

1.1-2+3-4+5-6+7-8

2.1-3+5-7+9-11+13-15

3.-1+3-5+7-9+11-13+15

4.2-4+6-8+10-12+14-16+18-20

5.-2+4-6+8-10+12-14+16-18+20

6.2-5+8-11+14-17+20-23+26

7.-1+5-9+13-17+21-25+29-33+37

8.1-5+9-....-81+85-89+93

9.2-4+6-8+....+202-204

10.1-6+11-16+21-....+176-181

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=?

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50.

Tính:a,(-40/41.0,32.17/20):64/75

b,-10/11.8/9+7/18.10/11

c,3/14:1/28-13/21:1/28+29/42:1/28-8

d,-12/7.15+2/7.(-15)+(-105).(2/3-4/5+1/7)

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50

NHỚ KẾT BẠN VỚI MÌNH NHA '-'

câu trả lời cho câu hỏi của Huong Le Thị Lan: 1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32.

=(1+32)+(2+31)+(3+30)+(4+29)+(5+28)+(6+27)+(7+26)+(8+25)+(9+24)+(10+23)+(11+22)+(12+21)+(13+20)+(14+19)+(15+18)+(16+17)

=33+33+33+33+33+33+33+33+33+33+33+33+33+33+33+33.    =33.16 (dấu chấm là dấu nhân)=528

a -5/9 + ( 17/20 - 4/9 )                              b (7/15  - 11/20 ). -25/3                           c ( 5/6 - 1/2 ).(8/15 - 3/15)                       d 11/12 + 7/16 : -3/4 - 13/12                                                            giup mimh voi minh tich cho