Bài 7: Tính nhanh: 1) 12/9+-4/10+-1/8+1/15 21/11/2021 Bởi Anna Bài 7: Tính nhanh: 1) 12/9+-4/10+-1/8+1/15
$\dfrac{12}{9} + \dfrac{-4}{10}+\dfrac{-1}{8}+\dfrac{1}{15}$ $ = \dfrac{4}{3} – \dfrac{2}{5} – \dfrac{1}{8} + \dfrac{1}{15}$ $ = \dfrac{20-6+1}{15} – \dfrac{1}{8}$ $ = 1 – \dfrac{1}{8}$ $ = \dfrac{7}{8}$ Bình luận
`12/9+(-4)/10+(-1)/8+1/15`
`⇔4/3-2/5+(-1)/8+1/15`
`⇔105/120=7/8`
$\dfrac{12}{9} + \dfrac{-4}{10}+\dfrac{-1}{8}+\dfrac{1}{15}$
$ = \dfrac{4}{3} – \dfrac{2}{5} – \dfrac{1}{8} + \dfrac{1}{15}$
$ = \dfrac{20-6+1}{15} – \dfrac{1}{8}$
$ = 1 – \dfrac{1}{8}$
$ = \dfrac{7}{8}$