Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
G=\(\frac{3}{2.5}+\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{2015.2017}\)
G=\(3.\left(\frac{1}{2.5}+\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{2015.2017}\right)\)
G=\(3.\left(\frac{1}{2}.\frac{1}{5}+\frac{1}{5}.\frac{1}{7}+\frac{1}{7}.\frac{1}{9}+...+\frac{1}{2013}.\frac{1}{2015}+\frac{1}{2015}.\frac{1}{2017}\right)\)
G=\(3.\left(\frac{1}{2}+\frac{1}{2017}\right)\)
G=1.5
Anh ko bik có đúng ko nữa lâu quá rồi. Em thông cảm nhé
Ta tách ra làm 2 ý nhé:
* \(1,11+0,19-1,32-\left(\frac{1}{2}+\frac{1}{3}\right):2\)
\(=1,3-1,32-\frac{5}{6}=-0,02-\frac{5}{6}=-\frac{1}{50}-\frac{5}{6}=-\frac{64}{75}\)
* \(\left(5\frac{7}{8}-2\frac{1}{4}-0,5\right):2\frac{23}{26}\)
\(\left(3\frac{5}{8}-\frac{1}{2}\right):2\frac{23}{26}=3\frac{1}{8}:2\frac{23}{26}=1\frac{1}{12}=\frac{13}{12}\)
VẬY TA CÓ: \(\frac{-64}{75}< x< \frac{13}{12}\)mà \(\left(x\inℕ\right)\)
\(\Rightarrow\)ta có x là số nguyên nằm giữa -0.8533... và 1,0833...
vậy ta có x là các số nguyên 0 và 1
MK KO CHẮC CHO LẮM NÊN BN CÓ THỂ THAM KHẢO Ý KIẾN MẤY BN KHÁC NHÉ.
K MK NHA. CHÚC BN HỌC TỐT. ^_^
Ta có \(\frac{7}{x}+\frac{4}{5.9}+\frac{4}{9.13}+...+\frac{4}{41.45}=\frac{29}{45}\)(đk : \(x\ne0\))
=> \(\frac{7}{x}+\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+...+\frac{1}{41}-\frac{1}{45}\right)=\frac{29}{45}\)
=> \(\frac{7}{x}+\left(\frac{1}{5}-\frac{1}{45}\right)=\frac{29}{45}\)
=> \(\frac{7}{x}+\frac{8}{45}=\frac{29}{45}\)
=> \(\frac{7}{x}=\frac{7}{15}\)
=> x = 15 (tm)
b) \(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{\left(2x+1\right)\left(2x+3\right)}=\frac{15}{93}\)
=> \(\frac{1}{2}\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{\left(2x+1\right)\left(2x+3\right)}\right)=\frac{15}{93}\)
=> \(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2x+1}-\frac{1}{2x+3}=\frac{10}{31}\)
=> \(\frac{1}{3}-\frac{1}{n+3}=\frac{10}{31}\)
=> \(\frac{1}{2x+3}=\frac{1}{93}\)
=> 2x + 3 = 93
=> 2x = 90
=> x = 45
Bài 1:
a) Ta có: \(\dfrac{2}{5}\cdot x+\dfrac{1}{3}=\dfrac{1}{5}\)
\(\Leftrightarrow\dfrac{2}{5}\cdot x=\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{-2}{15}\)
\(\Leftrightarrow x=\dfrac{-2}{15}:\dfrac{2}{5}=\dfrac{-2}{15}\cdot\dfrac{5}{2}\)
hay \(x=-\dfrac{1}{3}\)
Vậy: \(x=-\dfrac{1}{3}\)
b) Ta có: \(\dfrac{1}{5}+\dfrac{5}{3}:x=\dfrac{1}{2}\)
\(\Leftrightarrow\dfrac{5}{3}:x=\dfrac{1}{2}-\dfrac{1}{5}=\dfrac{3}{10}\)
\(\Leftrightarrow x=\dfrac{5}{3}:\dfrac{3}{10}=\dfrac{5}{3}\cdot\dfrac{10}{3}\)
hay \(x=\dfrac{50}{9}\)
Vậy: \(x=\dfrac{50}{9}\)
c) Ta có: \(\dfrac{4}{9}-\dfrac{5}{3}\cdot x=-2\)
\(\Leftrightarrow\dfrac{5}{3}x=\dfrac{4}{9}+2=\dfrac{22}{9}\)
\(\Leftrightarrow x=\dfrac{22}{9}:\dfrac{5}{3}=\dfrac{22}{9}\cdot\dfrac{3}{5}\)
hay \(x=\dfrac{22}{15}\)
Vậy: \(x=\dfrac{22}{15}\)
d) Ta có: \(\dfrac{5}{7}:x-3=\dfrac{-2}{7}\)
\(\Leftrightarrow\dfrac{5}{7}:x=\dfrac{-2}{7}+3=\dfrac{19}{21}\)
\(\Leftrightarrow x=\dfrac{5}{7}:\dfrac{19}{21}=\dfrac{5}{7}\cdot\dfrac{21}{19}\)
hay \(x=\dfrac{15}{19}\)
Vậy:\(x=\dfrac{15}{19}\)
Bài 5:
a: x(x-4)=0
=>\(\left[{}\begin{matrix}x=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)
b: Đề thiếu vế phải rồi bạn
Bài 6:
a: \(\left(-5\right)\cdot\left(-6\right)\cdot\left(-4\right)\cdot2\)
\(=-\left(2\cdot5\right)\cdot\left(4\cdot6\right)\)
\(=-24\cdot10=-240\)
b: \(\left(-3\right)\cdot2\cdot\left(-8\right)\cdot5\)
\(=3\cdot2\cdot8\cdot5\)
\(=\left(3\cdot8\right)\cdot\left(2\cdot5\right)\)
\(=24\cdot10=240\)
Bài 1:
a: \(\dfrac{25}{42}-\dfrac{20}{63}=\dfrac{75-40}{126}=\dfrac{35}{126}=\dfrac{5}{18}\)
b: \(\dfrac{9}{20}-\dfrac{13}{75}-\dfrac{1}{6}=\dfrac{135}{300}-\dfrac{52}{300}-\dfrac{50}{300}=\dfrac{33}{300}=\dfrac{11}{100}\)
1)a, \(0,5x-\frac{2}{3}x=\frac{7}{12}\) b) \(x:4\frac{1}{3}=-\frac{2}{5}\)
\(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\) \(x=-\frac{2}{5}.4\frac{1}{3}\)
\(-\frac{1}{6}x=\frac{7}{12}\) \(x=-\frac{26}{15}\)
\(x=\frac{-7}{2}\)
c) \(\left(\frac{3x}{7}+1\right):\left(-4\right)=-\frac{1}{28}\) d) \(x+30\%x=-1,3\)
\(\frac{3x}{7}+1=-\frac{1}{28}.\left(-4\right)\) \(x\left(1+30\%\right)=-1,3\)
\(\frac{3x}{7}+1=\frac{1}{7}\) \(1,3x=-1,3\)
\(\frac{3x}{7}=-\frac{6}{7}\) \(x=-1,3:1,3\)
\(x=-6.7:7:3\) \(x=-1\)
\(x=-2\)
Bài 2:
\(\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{2019.2021}=\frac{3}{2}\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{2019.2021}\right)\)
\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{2019}-\frac{1}{2021}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{2021}\right)\)
\(=\frac{3}{2}.\frac{2016}{10105}\)
\(=\frac{3024}{10105}\)