Tính hợp lý:5/6 • 1/3 + 1/2 • 3/4 • 5/3
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(\dfrac{5}{6}\cdot\dfrac{1}{3}+\dfrac{1}{2}\cdot\dfrac{3}{4}\cdot\dfrac{5}{3}\)
\(=\dfrac{5\cdot1}{6\cdot3}+\dfrac{1}{2}\cdot\dfrac{3\cdot5}{4\cdot3}\)
\(=\dfrac{5}{18}+\dfrac{1}{2}\cdot\dfrac{15}{12}\)
\(=\dfrac{5}{18}+\dfrac{1}{2}\cdot\dfrac{5}{4}\)
\(=\dfrac{5}{18}+\dfrac{1\cdot5}{2\cdot8}\)
\(=\dfrac{5}{18}+\dfrac{5}{8}\)
\(=\dfrac{65}{72}\)
= (2/5 + 3/5) + (6/9 + 1/3) + (7/4 + 1/4)
= 1 + (6/9 + 3/9) + 2 = 1 + 1 + 2 = 4
\(\dfrac{2}{5}+\dfrac{6}{9}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\\ =\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{7}{4}+\dfrac{1}{4}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)\\ =1+2+1=4\)
a. \(\dfrac{-2}{3}+\dfrac{-1}{5}+\dfrac{3}{4}-\dfrac{5}{6}-\dfrac{7}{10}\)
= \(\dfrac{-4}{6}+\dfrac{-2}{10}+\dfrac{3}{4}-\dfrac{5}{6}-\dfrac{7}{10}\)
= \(\dfrac{-3}{2}+\dfrac{1}{2}+\dfrac{3}{4}\)
= (-1) + \(\dfrac{3}{4}\)
= \(\dfrac{-4}{4}+\dfrac{3}{4}\)
= \(\dfrac{-1}{4}\)
\(13,=-1-1-...-1+101\)
Tổng trên có \(\left(100-1+1\right):2=50\) (số -1)
Vậy tổng trên \(=-50+101=51\)
\(A=\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+\frac{1}{6\times7}+\frac{1}{7\times8}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
\(=\frac{1}{2}-\frac{1}{8}\)
\(=\frac{3}{8}\)
Còn một câu hỏi nữa, làm sao để viết chữ phân số trong này thế?
`a, 4/9 + 2/5 + 5/9= (4/9 +5/9) + 2/5= 1 + 2/5= 5/5 + 2/5= 7/5`
`b, 6/13 + 5/8 + 7/13=(6/13 + 7/13) + 5/8=1+5/8= 8/8 + 5/8= 13/8`
`c, 5/11 + 6/25 + 66/121 = ( 5/11 + 66/121 ) + 6/25=1 + 6/25 = 25/25 + 6/25 = 31/25`
`d, 1/2 + 1/3 + 1/4 + 1/6 + 1/12 + 1/24= (1/2 + 1/4) +(1/3 + 1/6) + (1/12 + 1/24)= 3/4 + 1/2 + 1/8= 6/8 + 4/8 + 1/8= 11/8`
`@ yl`
\(\dfrac{5}{6}.\dfrac{1}{3}+\dfrac{5}{6}+\dfrac{3}{4}\)
\(=\dfrac{5}{6}.\left(\dfrac{1}{3}+\dfrac{3}{4}\right)=\dfrac{5}{6}.\dfrac{7}{12}=\dfrac{35}{72}\)