cho số n nguyên dương và các tổng sau:
S\(_1\)=1+\(\dfrac{1}{5}\), S\(_2\)=1+\(\dfrac{1}{5}+\dfrac{1}{5^2}\), S\(_3\)=1+\(\dfrac{1}{5}+\dfrac{1}{5^2}+\dfrac{1}{5^3}\), S\(_n\)=1+\(\dfrac{1}{5}+\dfrac{1}{5^2}+\dfrac{1}{5^3}+........+\dfrac{1}{5^n}\)
Chứng minh rằng: \(\dfrac{1}{5S_1^2}+\dfrac{1}{5^2S_2^2}+\dfrac{1}{5^3S^2_3}+.....+\dfrac{1}{5^nS^2_n}< \dfrac{35}{36}\)
Put the verbs in brackets into the present simple or presen continuous
1. A:I see you still have a toothache
B:Yes,I do.Actually,I.......(see) my dentist later
2.A:I......(think) of visiting Jim this afternoon.
B:Don't brother.I..........(think) he's on a business trip.
3.A:Why........(Greg/be) so rude today?
B:I have no idea.He.........(be) usually very polite.
4.A:Why..........(you/taste) the sauce?Does it need more pepper?
B:No.It .........(taste) great the way it is.
5.A:Why........(you/smell) the milk?
B:Because it..........(smell) of.We should throw it alway.
6.A:I see you ........(have) a new mobile phone
B:Yes,but I........(have) trouble understanding how it work
III. Sắp xếp lại câu bị xáo trộn
a) always/class/time/we/to/come/on.
→.......................................................................................
b) hours/week/often/does/how/he/many/a/work.
→.......................................................................................
c) not/American/uniforms/do/usually/school/wear/students.
→.......................................................................................
d) 10:00/at/Wednesday/Science/Nam/class/on/has.
→.......................................................................................
e) interesting/I/because/Math/it/like/is.
→.......................................................................................
i) like/what/does/subject/best/Tom.
→.......................................................................................
g) you/work/to/want/we/with.
→.......................................................................................
h) Know/you/do/likes/he/how/meat?
→.......................................................................................
l) There/excuse/a/!/post/is/me/near/office/here?
→.......................................................................................
m) That/you/the/ , / want/is/post/letter/to/Mai?
→.......................................................................................
n) Is/interestes/Mai/experiments/doing/in
→.......................................................................................
o) him/tell/I'll/please/call/after/5/again.
→.......................................................................................
k) Huong/be/November 20th/ , / twelve/on/will/Saturday.