Question

tính tổng:

1: 1+(-2)+3+(-4)+........+19+(-20)

2: 1- 2 +3 -4+......+99 - 100

3: 2 - 4+6 - 8+.....+48 - 50

4: -1 + 3 - 5 +7 -.....+97 - 99

5: 1 + 2 - 3 - 4 +.....+97 + 98 - 99 - 100

giải cụ thể hộ mk cái ak ^^

Answer 1

1))))))))) -1-1-1-1.......-1-1=X

20/2=10

X=-1*10=-10

2))))))))))))))

-1-1-1-......-1-1-1-1=C

100/2=50

c=50*-1=-50

3)))))

đề đúng https://olm.vn/hoi-dap/question/370687.html

đề sai 2-4+6-8....+46-48+50

-2-2-2-2..-2-2+50

1(2)3(4)5(6)7(8)

=>từ 1=>4 có 2_4_6_8_10 cặp

=>-2*10+50=-70

Answer 2

5, https://hoc24.vn/hoi-dap/question/176210.html

4

-1+3-5+7-...........+97-99

2+2+2+2+2...+2+2=v

(1)2(3)4(5)6(7)8(9)10

=>1_3;5_7;9_1;3_5;7_9(2 chục 1=>20) có 5 cặp

=>1=100 có 5*5=25cặp

=>c =2*25= 50

hoặc https://vn.answers.yahoo.com/question/index?qid=20110113160841AACCaTJ