Cho đoạn thẳng AB bằng 10cm trên tia AB lấy điểm M sao cho AM = 4cm trên tia BA lấy điểm N sao cho AN = 2cm
a.Hãy chứng tỏ M nằm giữa A và N
b.Tính độ dài đoan thẳng MN
c.Điểm M có là trung điểm của đoan thẳng AN không?Vì sao?
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\(2^{x+1}.2^{2014}=2^{2015}\)
\(\Rightarrow2^{x+1}=2^{2015}:2^{2014}\)
\(\Rightarrow2^{x+1}=2^1\)
\(\Rightarrow x+1=1\)
\(\Rightarrow x=0\)
\(6x+x=5^{11}:5^9+3^1\)
\(\Rightarrow7x=5^2+3\)
\(\Rightarrow7x=28\)
\(\Rightarrow x=4\)
- Nếu \(n⋮2\) thì \(\left(n+2018^{2019}\right)⋮2\) ( vì \(n⋮2;2018^{2019}⋮2\) )
\(\Rightarrow\left(n+2018^{2019}\right)\left(n+2019^{2018}\right)⋮2\)
- Nếu n không chia hết cho 2
\(\Rightarrow n:2\) dư 1
\(\Rightarrow n=2k+1\left(k\inℕ\right)\)
\(\Rightarrow n+2019^{2018}=2k+1+2019^{2018}⋮2\)
\(\Rightarrow\left(n+2018^{2019}\right)\left(n+2019^{2018}\right)⋮2\)
Vậy với mọi \(n\inℕ\) thì \(\left(n+2018^{2019}\right)\left(n+2019^{2018}\right)⋮2\)
* Nếu n là lẻ
(n+2018\(^{2019}\))(n+2019\(^{2018}\)), vì 2018\(^{2019}\)là chẵn nên n+2018\(^{2019}\)là lẻ, vì 2019\(^{2018}\)là lẻ , nên n+2019\(^{2018}\)là chẵn.
=>(n+2018\(^{2019}\))(n+2019\(^{2018}\)) là chẵn nên chia hết cho 2 (1)
* Nếu n là chẵn
(n+2018\(^{2019}\))(n+2019\(^{2018}\)), vì 2018\(^{2019}\)là chẵn nên n+2018\(^{2019}\)là chẵn, vì 2019\(^{2018}\)là lẻ , nên n+2019\(^{2018}\)là lẻ.
=>(n+2018\(^{2019}\))(n+2019\(^{2018}\)) là chẵn nên chia hết cho 2 (2)
Từ (1) và (2) => với mọi số tự nhiên n thì (n+2018\(^{2019}\))(n+2019\(^{2018}\)) chia hết cho 2
chúc học tốt
Gọi \(3n+2;5n+3=d\left(d\inℕ^∗\right)\)
\(3n+2⋮d\Rightarrow15n+10⋮d\)
\(5n+3⋮d\Rightarrow15n+9⋮d\)
Suy ra : \(15n+10-15n-9⋮d\)
\(1⋮d\)hay \(d\in\left\{1\right\}\)
Tương tự mấy phần kia :D
#Tách ra bạn ơi , đáp án lẫn lộn quá
TEST 1
II. Choose the best answer.
1. My father always.. ......the news on the radio in the morning
. A. listen to B. watches
2. My friends, Hoa and Ba,....... English on Monday and Friday.
A. not have B. isn't have C. Don't have
3. You......must..stop when the traffic light turns red.
A. go
4. My mother goes to the supermarket on foot.
5. The meeting is very important, so you.... .be late!
C. should D. shouldn't
8. Which city is..larger. .Ha Noi or Ho Chi Minh City?
A. large B. larger C. largest D. the largest
10. I will......my lucky money in my piggy bank.
A. keep
r V. Rewrite the second sentence so that it has the same meaning.
1. My class has thirty five students.
There are thirty five students in my class
2. In the garden, there are many flowers and fruits.
The garden has many flowers and fruits
3. My father often rides motorbike to work.
My father goes by motorbike
4. The hotel is behind the hospital
The hospital is in front of the hotel
II. Choose the correct answers
1. Do you know Janelyn? Yes, of course, I (met/ meet/ is meeting) her every day!
2. I ( am / was / were ) very happy on my last vacation.
3. Where is Tom? Ah! he (is playing/ plays/played) football with his friends in the garden
5. He ( doesn't/ won't / didn't) come here tomorrow.
6. (When / where / What time ) did you see her ?- Yesterday morning.
7. We ( are visiting / will visit / visit / visited) Ha Long Bay last summer vacation.
8. Lan sometimes (goes / go / went/ is going ) to the zoo.
9. When they (was / will be / were / are ) children, they often played with each other.
10. Yesterday, I ( am buying / going to buy / buy / bought) many gifts for him on the trip to Ha Noi.