![](https://rs.olm.vn/images/avt/0.png?1311)
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)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{10}{15}-\dfrac{6}{15}=\dfrac{14}{15}\)
\(b.\dfrac{-2}{5}.\dfrac{5}{8}+\dfrac{5}{8}.\dfrac{3}{5}=\dfrac{5}{8}.\left(\dfrac{-2}{5}+\dfrac{3}{5}\right)=\dfrac{5}{8}.\dfrac{1}{5}=\dfrac{1}{8}\)
\(c.25\%-1\dfrac{1}{2}+0,5.\dfrac{12}{5}=\dfrac{1}{4}-\dfrac{3}{2}+\dfrac{6}{5}=-\dfrac{1}{20}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)
\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)
\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1.
\(a,\dfrac{1}{3}+\dfrac{1}{4}=\dfrac{4}{12}+\dfrac{3}{12}=\dfrac{7}{12}\)
\(b,\dfrac{-2}{5}+\dfrac{7}{21}=\dfrac{-42}{105}+\dfrac{35}{105}=\dfrac{-77}{105}=\dfrac{-11}{15}\)
\(c,\dfrac{3}{8}+\dfrac{-5}{6}=\dfrac{18}{48}+\dfrac{-40}{48}=\dfrac{-22}{48}=\dfrac{-11}{24}\)
\(d,\dfrac{-3}{4}+\dfrac{2}{5}=\dfrac{-15}{20}+\dfrac{8}{20}=\dfrac{-7}{20}\)
\(e,\dfrac{1}{6}+\dfrac{-3}{2}=\dfrac{2}{12}+\dfrac{-18}{12}=\dfrac{16}{12}=\dfrac{4}{3}\)
\(f,\dfrac{-2}{5}+\dfrac{-4}{3}=\dfrac{-6}{15}+\dfrac{-20}{15}=\dfrac{-26}{15}\)
\(g,\dfrac{1}{8}+\dfrac{-3}{4}=\dfrac{4}{32}+\dfrac{-24}{32}=\dfrac{20}{32}=\dfrac{5}{8}\)
\(h,\dfrac{-3}{4}+\dfrac{3}{7}=\dfrac{-21}{28}+\dfrac{12}{28}=\dfrac{-9}{28}\)
\(i,\dfrac{-3}{4}+\dfrac{-4}{5}=\dfrac{-15}{20}+\dfrac{-16}{20}=\dfrac{-31}{20}\)
\(k,\dfrac{-5}{25}+\dfrac{-7}{14}=\dfrac{-70}{350}+\dfrac{-175}{350}=\dfrac{-245}{350}=\dfrac{-7}{10}\)
\(l,\dfrac{6}{21}+\dfrac{-3}{15}=\dfrac{90}{315}+\dfrac{-63}{315}=\dfrac{27}{315}=\dfrac{3}{35}\)
\(m,\dfrac{3}{4}-\dfrac{5}{8}+\dfrac{1}{2}=\dfrac{24}{32}-\dfrac{20}{32}+\dfrac{1}{2}=\dfrac{4}{32}+\dfrac{1}{2}=\dfrac{1}{8}+\dfrac{1}{2}=\dfrac{2}{16}+\dfrac{8}{16}=\dfrac{10}{16}=\dfrac{5}{8}\)
\(n,\dfrac{-3}{12}-\dfrac{1}{-4}+\dfrac{-2}{6}=\dfrac{-1}{4}-\dfrac{1}{-4}+\dfrac{-1}{3}=0+\dfrac{-1}{3}=\dfrac{-1}{3}\)
\(p,\dfrac{1}{3}+\dfrac{-3}{4}-\dfrac{5}{12}=\dfrac{4}{12}+\dfrac{-9}{12}-\dfrac{5}{12}=\dfrac{-5}{12}-\dfrac{5}{12}=\dfrac{-10}{12}=\dfrac{-5}{6}\)
Bài 2:
\(a,\dfrac{3}{5}+x=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}-\dfrac{3}{5}\)
\(x=\dfrac{7}{30}\)
\(b,x-\dfrac{1}{4}=\dfrac{-5}{8}\)
\(x=\dfrac{-5}{8}+\dfrac{1}{4}\)
\(x=\dfrac{-3}{8}\)
\(c,x-\dfrac{2}{3}=\dfrac{7}{12}\)
\(x=\dfrac{7}{12}+\dfrac{2}{3}\)
\(x=\dfrac{5}{4}\)
\(d,x+\dfrac{-7}{15}=-1\dfrac{1}{20}\)
\(x=-1\dfrac{1}{20}-\dfrac{-7}{15}\)
\(x=\dfrac{-7}{12}\)
\(e,x-\dfrac{1}{2}=\dfrac{-3}{4}\)
\(x=\dfrac{-3}{4}+\dfrac{1}{2}\)
\(x=\dfrac{-1}{4}\)
\(f,x-\dfrac{3}{4}=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}+\dfrac{3}{4}\)
\(x=\dfrac{5}{4}\)
\(g,x-\dfrac{1}{4}=\dfrac{5}{8}\cdot\dfrac{2}{3}\)
\(x-\dfrac{1}{4}=\dfrac{5}{12}\)
\(x=\dfrac{5}{12}+\dfrac{1}{4}\)
\(x=\dfrac{2}{3}\)
\(h,\dfrac{4}{5}-x=\dfrac{-8}{35}\)
\(x=\dfrac{4}{5}-\dfrac{-8}{35}\)
\(x=\dfrac{36}{35}\)
#YVA
![](https://rs.olm.vn/images/avt/0.png?1311)
150 : \(x\) = 9 - (-1)
150 : \(x\) = 9 + 1
150 : \(x\) = 10
\(x\) = 150 : 10
\(x\) = 15
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Tỉ số giữa số bi của AN và Bình là:
\(\dfrac{3}{14}:\dfrac{5}{28}=\dfrac{3}{14}\cdot\dfrac{28}{5}=\dfrac{6}{5}\)
Số viên bi của An là: 15:1x6=90(viên)
Số viên bi của Bình là 90-15=75(viên)
Số viên bi của An là: 90 viên
Số viên bi của Bình là 75 viên