a) Xét △ \(C N B\) (vuông tại \(N\)) và △ \(A N F\) (vuông tại \(N\)) có:

\(N B = N F\) (gt)
\(\) \(NB\) chung
Vậy △ C N B = △ A N F ( cạnh huyền - góc nhọn )

=> CB=AF (hai cạnh tương ứng)

b) Theo câu a, ta có △ CNB = △ ANF

=> \(C N = N A\) (hai cạnh tương ứng).

Vì \(C N = N A\) và \(N B = N F\) nên \(N\) và \(B\) cùng cách đều hai đầu mút của đoạn thẳng \(C A\).

Suy ra: \(N B\) là đường trung trực của đoạn thẳng \(C A\).

Vậy: \(A B = M E\).

Không có đáp án nào đúng

* Tham khảo
Social media platforms have many impacts on students’ study and physical development. On the positive side, social media can help students access information quickly and communicate with teachers and friends to discuss lessons. Many educational pages and videos also help students understand difficult subjects better. However, excessive use of social media can negatively affect students’ academic performance. Students may spend too much time scrolling through posts, watching videos, or chatting instead of focusing on their homework and revision. As a result, their concentration and learning efficiency may decrease. In addition, using phones or computers for long hours can affect students’ physical health. It may lead to eye strain, poor posture, lack of sleep, and less physical activity. When students spend more time online, they may also exercise less, which can slow down their physical development. Therefore, students should learn to use social media wisely and balance their study time, online activities, and physical exercise.

\(a)\) \(A=2+2^2+2^3+2^4+\cdots+2^{101}+2^{102}\)

\(\Rightarrow2A=2^2+2^3+2^4+2^5+\cdots+2^{102}+2^{103}\)

\(\Rightarrow2A-A=\left(2^2+2^3+2^4+2^5+\cdots+2^{102}+2^{103}\right)-\left(2+2^2+2^3+2^4+\cdots+2^{101}+2^{102}\right)\)

\(\Rightarrow A=2^{103}-2\)

\(b)\) \(B=1+3+3^2+\cdots+3^{50}\)

\(\Rightarrow3B=3+3^2+3^3+\ldots+3^{51}\)

\(\Rightarrow3B-B=\left(3+3^2+3^3+\cdots+3^{51}\right)-\left(1+3+3^2+\cdots+3^{50}\right)\)

\(\Rightarrow2B=3^{51}-1\)

\(\Rightarrow B=\frac{3^{51}-1}{2}\)

\(c)\) \(C=\frac13+\frac16+\frac{1}{10}+\frac{1}{15}+\cdots+\frac{1}{45}\) ​

\(= \frac{2}{6} + \frac{2}{12} + \frac{2}{20} + . . . + \frac{2}{90}\)

\(= 2 \left(\right. \frac{1}{6} + \frac{1}{12} + \frac{1}{20} + . . . + \frac{1}{90} \left.\right)\)

\(= 2 \left(\right. \frac{1}{2} - \frac{1}{3} + \frac{1}{3} - \frac{1}{4} + . . . + \frac{1}{9} - \frac{1}{10} \left.\right)\)

\(=2\left(\right.\frac{1}{2}-\frac{1}{10}\left.\right)=2\cdot\frac{2}{5}=\frac{4}{5}\)

* Sửa

Số học sinh lớp 5A là:

\(5:\frac17=35\) ( bạn )

Lời giải

Ở kì 2, tỉ số giữa học sinh nam và cả lớp là:

2 : ( 2 + 7 ) = \(\frac27\)

Phần số chỉ 5 bạn nam chuyển đi là:

\(\frac37-\frac27=\frac17\)

Số học sinh lớp 5A là:

\(5+\frac17=35\) ( bạn )

Đáp số:...

\(32\times1,25\times2,5+5,4\times8,7+5,4\times3,3-10,8\)

\(=8\times4\times1,25\times2,5+5,4\times\left(8,7+3,3\right)-5,4\times2\)

=\(\left(1,25\times8\right)\times\left(2,5\times4\right)+5,4\times\left(8,7+3,3-2\right)\)

\(=10\times10+5,4\times10\)

\(=100+54\)

\(=154\)

1. Mandy is a pretty girl

2.The class is terrible today

3.Maxisa is good in her class

4.You can easily open this tin

5.It's a terrible day today

6.She sings the song well

7.He is a careful driver

8.He drives the car carefull

9.The dog barks loudly.

\(67,36\times101-67,36\times1\)
\(=67,36\times\left(101-1\right)\)

\(=67,36\times100\)

\(=6736\)

Đáp án: Ti vi