Question

a) x² :\(\frac{16}{11}\)=\(\frac{11}{4}\)

b)Tính tổng:\(\frac{1}{1\cdot4}\)+\(\frac{1}{4\cdot7}\)+\(\frac{1}{7\cdot10}\)+\(\frac{1}{13\cdot16}\)+\(\frac{1}{16\cdot19}\)

Giúp mik giải nha, cảm ơn mn nhiều ạ

 

Answer 1

Trả lời

a)

\(x^2:\frac{16}{11}=\frac{11}{4}\)

\(\Leftrightarrow x^2=\frac{11}{4}\cdot\frac{16}{11}\)

\(\Leftrightarrow x^2=\frac{16}{4}\)

\(\Leftrightarrow x^2=\left(\frac{4}{2}\right)^2\)

\(\Leftrightarrow x=\frac{4}{2}\)

Vậy x=\(\frac{4}{2}\)

b) (bạn thiếu nhóm \(\frac{1}{10\cdot13}\))

Đặt \(A=\frac{1}{1\cdot4}+\frac{1}{4\cdot7}+\frac{1}{7\cdot10}+\frac{1}{10\cdot13}+\frac{1}{13\cdot16}+\frac{1}{16\cdot19}\)

\(\Rightarrow3A=3\left(\frac{1}{1\cdot4}+\frac{1}{4\cdot7}+\frac{1}{7\cdot10}+\frac{1}{10\cdot13}+\frac{1}{13\cdot16}+\frac{1}{16\cdot19}\right)\)

\(\Rightarrow3A=\frac{3}{1\cdot4}+\frac{3}{4\cdot7}+\frac{3}{7\cdot10}+\frac{3}{10\cdot13}+\frac{3}{13\cdot16}+\frac{3}{16\cdot19}\)

\(\Rightarrow3A=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}+\frac{1}{19}\)

\(\Rightarrow3A=1-\frac{1}{19}\Leftrightarrow3A=\frac{18}{19}\)

\(\Rightarrow A=\frac{18}{19}:3\Leftrightarrow A=\frac{6}{19}\)

Answer 2

a,x​=2

b,=6/19

Answer 3

a) \(x^2:\frac{16}{11}=\frac{11}{4}\)

\(\Rightarrow x^2=\frac{11}{4}.\frac{6}{11}\)

\(\Rightarrow x^2=\frac{3}{2}\)

\(\Rightarrow x=\sqrt{\frac{3}{2}}\)

b) Đề thiếu

\(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+\frac{1}{13.16}+\frac{1}{16.19}\)

\(=\frac{1}{3}\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}\right)\)

\(=\frac{1}{3}\left(1-\frac{1}{19}\right)\)

\(=\frac{1}{3}.\frac{18}{19}\)

\(=\frac{6}{19}\)

Answer 4

câu b trước nha

=\(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}\)\(\frac{1}{19}\)

=\(\frac{1}{1}-\frac{1}{19}\)

=\(\frac{18}{19}\)

a)\(x^2=\frac{11}{4}\times\frac{16}{11}\)

\(x^2=4\)

\(\Rightarrow x=2\)

Answer 5

a, \(x^2:\frac{16}{11}=\frac{11}{4}\)

\(x^2=4\)

\(x^2=2^2\)

\(\Rightarrow x=2\)

b.\(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{13.16}+\frac{1}{16.19}\)

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{16}-\frac{1}{19}\)

\(=1-\frac{1}{19}\)

\(=\frac{18}{19}\)