21 7 phần 19 - 3 7 phần 19 =
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{20}{15}+\frac{3}{7}\)
\(\frac{15}{34}+\frac{1}{3}+\frac{19}{34}+\left(-\frac{4}{3}\right)+\frac{3}{7}\)
\(\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{1}{3}-\frac{4}{3}\right)+\frac{3}{7}\)
\(1+\left(-1\right)+\frac{3}{7}\)
\(=0+\frac{3}{7}=\frac{3}{7}\)
\(\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{20}{15}+\frac{3}{7}\)
\(=\)\(\frac{15}{34}+\frac{1}{3}+\frac{19}{34}+\left(-\frac{4}{3}\right)+\frac{3}{7}\)
\(=\)\(\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{1}{3}-\frac{4}{3}\right)+\frac{3}{7}\)
\(=\)\(1+\left(-1\right)+\frac{3}{7}\)
\(=\)\(0+\frac{3}{7}\)
\(=\)\(\frac{3}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Đề như này?: \(21\frac{7}{19}\div1\frac{1}{5}-3\frac{7}{19}\div1\frac{1}{5}\)
\(=\left(21\frac{7}{19}-3\frac{7}{19}\right)\div1\frac{1}{5}\)
\(=\left(\frac{406}{19}-\frac{64}{19}\right)\div\frac{6}{5}\)
\(=18\div\frac{6}{5}\)
\(=15\)
![](https://rs.olm.vn/images/avt/0.png?1311)
A = \(\dfrac{2}{3.5}\) + \(\dfrac{2}{5.7}\) + \(\dfrac{2}{7.9}\) + ... + \(\dfrac{2}{19.21}\)
A = \(\dfrac{1}{3}\) - \(\dfrac{1}{5}\) + \(\dfrac{1}{5}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{1}{9}\) + ... + \(\dfrac{1}{19}\) - \(\dfrac{1}{21}\)
A = \(\dfrac{1}{3}\) - \(\dfrac{1}{21}\)
A = \(\dfrac{2}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
7/19 nhân 8/11 cộng 3/11 nhân 7/19 trừ 2
= 7/19 nhân ( 8/11 cộng 3/11) trừ 2
=7/19 nhân 1 trừ 2
=7/19 trừ 2 = 7/19 trừ 38/19 = -31/19
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{7}{19}\times\frac{1}{3}+\frac{7}{19}\times\frac{2}{3}\)
\(=\frac{7}{19}\times\left(\frac{1}{3}+\frac{2}{3}\right)\)
\(=\frac{7}{19}\times1\)
\(=\frac{7}{19}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{3}{4}+\frac{5}{9}:\frac{4}{5}=\frac{3}{4}+\frac{5}{9}\times\frac{5}{4}\)
\(=\frac{3}{4}+\frac{25}{36}=\frac{27}{36}+\frac{25}{36}=\frac{27+25}{36}=\frac{52}{36}=\frac{13}{9}\)
\(\frac{7}{19}\times\frac{4}{7}-\frac{7}{19}\times\frac{3}{7}=\frac{7}{19}\times\left(\frac{4}{7}-\frac{3}{7}\right)\)
\(=\frac{7}{19}\times\frac{1}{7}=\frac{1}{19}\)
\(21\frac{7}{19}-3\frac{7}{19}=18\)