Tham khảo
`a) \frac{a}{2}+\frac{1}{b}=\frac{3}{2}(b \ne 0)`
`⇒\frac{1}{b}=\frac{3}{2}-\frac{a}{2}`
`⇒\frac{1}{b}=\frac{3-a}{2}`
`⇒b(3-a)=2`
`⇒b,3-a∈Ư(2)={±1,±2}`
Ta có bảng:
$\left[\begin{array}{ccc}b&1&-1&2&-2\\3-a&2&-2&1&-1\\a&1&5&2&4\end{array}\right]$
Vậy `(a,b)=(1,1);(5,-1);(2,2);(4,-2)`
`b) \frac{7}{15}-(\frac{7}{16}+\frac{7}{17})-(\frac{7}{18}-\frac{7}{16})-\frac{7}{9}`
`=7.(\frac{1}{15}-\frac{1}{16}-\frac{1}{17}-\frac{1}{18}+\frac{7}{16}-\frac{1}{9}`
`=7.(\frac{1}{15}-\frac{1}{17}-\frac{1}{18}-\frac{1}{9})`
`=7.(\frac{-27}{170})`
`=\frac{-189}{170}`
`\text{©CBT}`
