\(-2\frac{7}{15}=\frac{-2\cdot15+7}{15}=\frac{-23}{15}\)

Vậy hỗn số \(-2\frac{7}{15}\)viết dưới dạng phần số là \(\frac{-23}{15}\)

\(-2\frac{7}{5}=\frac{-2.15+7}{15}=\frac{-23}{15}\)

Vậy hỗn số \(-2\frac{7}{15}\) viết dưới dạng phân số là : \(\frac{-23}{15}\)

a/\(A=\left(3+5\right)^2=8^2=64\)

\(B=3^2+5^2=9+25=34\)

\(\Rightarrow A>B\)

b/ \(C=\left(3+5\right)^3=8^3=512\)

\(D=3^3+5^3=27+125=152\)

\(\Rightarrow C>D\)

a/ A= (3+5)² = 8² = 64

   B = 3² + 5² = 9 + 25 = 34

vì 64>34 => A > B

b/ C = (3+5)³ = 8³ = 512

    D = 3³ + 5³ = 27 + 125 = 152

Vì 512>152 => C > D

320km

3200 hm = 320 km

\(x^2-5x=-1\Leftrightarrow x^2-5x-\left(-1\right)=0\)

\(\Rightarrow x=\frac{-\left(-5\right)\pm\sqrt{\left(-5\right)^2-4\cdot1\cdot1}}{2\cdot1}\)

\(\Leftrightarrow x=\frac{5\pm\sqrt{25-4\cdot1\cdot1}}{2\cdot1}\)

\(\Leftrightarrow x=\frac{5\pm\sqrt{21}}{2}\)

a/ A = 8²

A = 64

B = 9 + 25, B = 34

b/ C = 8³, CC = 512

D = 27 + 125

D = 152

29236538

Answer:

Có \(a+b+c=3\)

\(\Rightarrow\left(a+b+c\right)^2=3^2\)

      \(a^2+b^2+c^2+2ab+2bc+2ac=9\left(\text{*}\right)\) 

Mà đề ra \(\frac{1}{a}+\frac{1}{b}+\frac{1}{c}=0\)

\(\Leftrightarrow\frac{bc}{abc}+\frac{ac}{abc}+\frac{ab}{abc}=0\)

\(\Leftrightarrow\frac{bc+ac+ab}{abc}=0\)

\(\Leftrightarrow bc+ac+ab=0\left(\text{*}\text{*}\right)\)

Thay (**) vào (*), được \(a^2+b^2+c^2=9\)

6 + 7= 13

7 : 7=1

7 + 7=1

HT^^ 

1. The van is running fast.

2. Laughing is good for health.

3. Refer to exercise 3, page 24 of your textbook.

4. Have is a verb.

5. Every day we take the ferry to school.