một vé báo cáo

ko chỉ 1 mà là 9 vé báo cáo đăng linh tinh :(

18:2,4=7,5

38:62,5=0,608

207:31,6=6,56

18 : 2,4 = 7,5

38 : 62,5 = 0,(5)

207 : 31,6 = 9.58(3)

Câu a

\(S=\frac{3-1}{1x3}+\frac{5-3}{3x5}+\frac{7-5}{5x7}+...+\frac{2019-2017}{2017x2019}.\)

\(S=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}=1-\frac{1}{2019}=\frac{2018}{2019}\)

Câu b

\(A=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+\frac{1}{3^4}+...+\frac{1}{3^6}+\frac{1}{3^7}\)

\(3A=1+\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^5}+\frac{1}{3^6}\)

\(2A=3A-A=1-\frac{1}{3^7}\Rightarrow A=\frac{1}{2}-\frac{1}{2.3^7}\)

Make up sentences using the words and phrase given:

1. She / like / listen / to music / in / her / free time.

=> She likes listening to music in her free time.

2. Nam / think / swimming / more exciting / than / playing chess.

=> Nam thinks swimming is more exciting than playing chess.

Vì điểm M nằm trong góc AOB nên:

góc AOM+góc MOB=góc AOB

\(\Rightarrow\)1/3 góc MOB+góc MOB= góc AOB

\(\Rightarrow\)4/3 góc MOB= góc AOB

\(\Rightarrow\)góc MOB=góc AOB:4/3=120độ:4/3=90độ.

\(\Rightarrow\)góc AOM=120 độ-90 độ=30 độ.

Vậy:góc AOM=30 độ,góc MOB=90 độ

1/ 
1/2! +2/3! +3/4! +... + 99/100! 
= (1/1! -1/2!) + (1/2! - 1/3!) + (1/3! -1/4!) + .... + (1/99! -1/100!) 
=1 - 1/100! <1