1:

#include <bits/stdc++.h>

using namespace std;

long long t,i,n;

int main()

{

cin>>n;

t=0;

for (i=1; i<=n; i++) t+=i;

cout<<t;

return 0;

}

Bài 2: 

#include <bits/stdc++.h>

using namespace std;

long long n,i,t;

int main()

{

cin>>n;

t=0;

for (i=1; i<=n; i++)

if (i%2==0) t+=i;

cout<<t;

return 0;

}

Bài 3: 

#include <bits/stdc++.h>

using namespace std;

long long n,i,t;

int main()

{

cin>>n;

t=0;

for (i=1; i<=n; i++)

if (i%2!=0) t+=i;

cout<<t;

return 0;

}

Bài 4: 

#include <bits/stdc++.h>

using namespace std;

long long n,i,t;

int main()

{

cin>>n;

t=0;

for (i=1; i<=n; i++)

if (i%3==0) t+=i;

cout<<t;

return 0;

}

Bài 5: 

#include <bits/stdc++.h>

using namespace std;

long long n,i,t;

int main()

{

cin>>n;

t=1;

for (i=1; i<=n; i++)

t*=i;

cout<<t;

return 0;

}

???

Bài 37:

a: \(\overrightarrow{AB}=\left(4;-8\right)\)

\(\overrightarrow{BC}=\left(5;5\right)\)

????

a, Áp dụng định lý Ta-lét ta có:
\(\dfrac{AD}{DB}=\dfrac{AE}{EC}\Rightarrow\dfrac{4}{x}=\dfrac{5}{10}\Rightarrow x=4:\dfrac{1}{2}\Rightarrow x=8\)

Áp dụng hệ quả định lý Ta-lét ta có:

\(\dfrac{AE}{AC}=\dfrac{DE}{BC}\Rightarrow\dfrac{5}{15}=\dfrac{6}{y}\Rightarrow y=6:\dfrac{1}{3}\Rightarrow y=18\)

b, Áp dụng định lý phân giác ta có:
\(\dfrac{DB}{DC}=\dfrac{AB}{AC}\Rightarrow\dfrac{5}{6}=\dfrac{10}{x}\Rightarrow x=10:\dfrac{5}{6}\Rightarrow x=12\)

a: A=x^2+4x+4+5

=(x+2)^2+5>=5

Dấu = xảy ra khi x=-2

b: =3/2(x^2+2/3x+2/3)

=3/2(x^2+2*x*1/3+1/9+5/9)

=3/2(x+1/3)^2+15/18>=15/18=5/6

Dấu = xảy ra khi x=-1/3

e: =x^2-2x+1+4

=(x-1)^2+4>=4

Dấu = xảy ra khi x=1

f: =2(x^2-3x)

=2(x^2-3x+9/4-9/4)

=2(x-3/2)^2-9/2>=-9/2

Dấu = xảy ra khi x=3/2

h: =-(x^2-4x-3)

=-(x^2-4x+4-7)

=-(x-2)^2+7<=7

Dấu = xảy ra khi x=2

my parents are enjoying their summer vacation in Miami

they are drinking coffee with friends

Look! it's starting to rain!

They are buying some cakes for the kids at home

What is your brother doing?

what

how

1. What did the people do when you were there

2. I visited Dalat with my parents.

3. What do you think of Tam?

4. The life in countryside is peaceful and more than I expected

1.What did the people do when you were there?

2.I visited Da Lat with my parents.

3.What do you think of Tam?

4.The life in the countryside is more peaceful than I expected.