\(2n+1⋮6-n\)
\(\Rightarrow\dfrac{2n+1}{6-n}\in Z\)
\(=\dfrac{2\left(6-n\right)+11}{6-n}=2+\dfrac{11}{6-n}\)
\(\Rightarrow6-n\in U\left(11\right)\)
Bảng:
| 6-n | -1 | 1 | -11 | 11 |
| n | 7 | 5 | 17 | -5 |
Thử lại:
Thay \(n=7\)
\(\Rightarrow\dfrac{2n+1}{6-n}=\dfrac{2\left(7+1\right)}{6-7}=-16\) (t/m)
Tương tự thay hết các n trong bảng
Vậy \(n\in\left\{7;5\right\}\)
Tìm x:
\(\dfrac{5}{6}.|\dfrac{3}{8}-x|-\left(\dfrac{-7}{8}+\dfrac{11}{12}-\dfrac{5}{6}\right)=-\left(\dfrac{-1}{2}\right)^2\)
Bài 1: Thực hiện phép tính (hợp lý nếu có thể)
\((6\dfrac{4}{9}+3\dfrac{7}{11})-4\dfrac{4}{9}\)
\(1\dfrac{1}{3}-2\dfrac{5}{6}-\dfrac{6}{11}+3:5\%\)
\(4\dfrac{3}{4}-0,37+\dfrac{1}{8}-1,28-2,5+3\dfrac{1}{12}\)
\(\dfrac{5}{7}.\dfrac{5}{11}+\dfrac{5}{7}.\dfrac{2}{11}-\dfrac{5}{7}.\dfrac{14}{11}\)
\(\dfrac{\left(2^3.5.7\right).\left(5^2.7^3\right)}{\left(2.5.7^2\right)^2}\)
Tìm \(n\in N\) biết :
\(\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{12}+..............+\dfrac{2}{n\left(n+1\right)}=\dfrac{2003}{2004}\)
Tính giá trị biểu thức :
\(\dfrac{1}{2}-\left(\dfrac{1}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{4}+\dfrac{2}{4}+\dfrac{3}{4}\right)-\left(\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}\right)+\left(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{3}{6}+\dfrac{4}{6}+\dfrac{5}{6}\right)-\left(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{4}{7}+\dfrac{5}{7}+\dfrac{6}{7}\right)+...+\left(100+...+\dfrac{99}{100}\right)\)
Tìm các số nguyên x, y thỏa mãn :
a) \(\dfrac{5}{7}-1\dfrac{4}{7}\left(450\%+\dfrac{2}{3}x\right)=-\dfrac{1}{14}\)
b) 100 = 6 .7|x+2| - 194
c) 2x + 3 = y2 ( với x, y \(\in\) N )
BT3: Tìm x, biết:
7) \(\dfrac{-5}{17}+\dfrac{3}{17}\le\dfrac{x}{17}\le\dfrac{13}{17}+\dfrac{-11}{17}\)
8) \(\dfrac{2}{3}\left(\dfrac{1}{2}+\dfrac{3}{4}-\dfrac{1}{3}\right)\le\dfrac{x}{18}\le\dfrac{7}{3}\left(\dfrac{1}{2}-\dfrac{1}{6}\right)\)
A= \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)
B=\(\left(10\dfrac{2}{9}+2\dfrac{3}{5}\right)-6\dfrac{2}{9}\)
- Giúp con ngu lâu dốt bền môn toán này với :(
\(\dfrac{0,8:\left(\dfrac{4}{5}.1,25\right)}{0,64-\dfrac{1}{25}}\)+\(\dfrac{\left(100-\dfrac{2}{5}\right):\dfrac{4}{7}}{6.\left(\dfrac{5}{9}-3\dfrac{1}{4}\right).2\dfrac{2}{17}}\)
help me, please
Nhanh lên nha, mai mình đi học rùi
Thank you so much
Tìm số nguyên n sao cho 2n-1 là bội của n+3. Mình làm thế này có đúng không?
Ta có: \(\frac{2n-1}{n+3}=\frac{2n-7+6}{n+3}=\frac{2n+6}{n+3}-\frac{7}{n+3}=\frac{2\left(n+3\right)}{n+3}=2-\frac{7}{n+3}\Rightarrow n+3\inƯ_{\left(7\right)}\)
Ư(7) = {-7; -1; 1;7}
Ta có:
| n+3 | -7 | -1 | 1 | 7 |
| n | -10 | -4 | -2 | 4 |
Vậy:\(n\in\left\{-10;-4;-2;4\right\}\)