tính hợp lí
(1/2-13/14):5/7-(-2/21+1/7):5/7
K
Khách
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Những câu hỏi liên quan
2 tháng 4 2021
c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)
\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)
\(=1-2=-1\)
2 tháng 4 2021
Giải:
a)-1/12+4/3=-1/12+16/12=15/12=5/4
b)(-4/14-3/15)-(1/5-20/35-(-1)).7
=-17/35-22/35.7
=-17/35-22/5
=-171/35
c)3/5+-5/20+30/75+-7/4
=3/5+-1/4+2/5+-7/4
=(3/5+2/5)+(-1/4+-7/4)
=1+-2
=-1
d)5/6.-12/14+7/13
=-5/7+7/13
=-16/91
e)2/-9-5/-36-1/4
=-1/12-1/4
=-1/3
f)2/23+-5/12+7/18+21/23+-7/12
=(2/23+21/23)+(-5/12+-7/12)+7/18
=1+-1+7/18
=7/18
DT
Đỗ Thanh Hải
CTVVIP
11 tháng 3 2021
a) \(\dfrac{\dfrac{3}{14}-\dfrac{3}{17}+\dfrac{3}{19}}{\dfrac{5}{19}+\dfrac{5}{14}-\dfrac{5}{17}}=\dfrac{3\left(\dfrac{1}{14}-\dfrac{1}{17}+\dfrac{1}{19}\right)}{5\left(\dfrac{1}{14}-\dfrac{1}{17}+\dfrac{1}{19}\right)}=\dfrac{3}{5}\)
DT
Đỗ Thanh Hải
CTVVIP
11 tháng 3 2021
c) \(\dfrac{\dfrac{2}{7}+\dfrac{2}{5}+\dfrac{2}{17}-\dfrac{2}{193}}{\dfrac{3}{7}+\dfrac{3}{5}+\dfrac{3}{17}-\dfrac{3}{293}}=\dfrac{2\left(\dfrac{1}{7}+\dfrac{1}{5}+\dfrac{1}{17}-\dfrac{1}{193}\right)}{3\left(\dfrac{1}{7}+\dfrac{1}{5}+\dfrac{1}{17}-\dfrac{1}{193}\right)}=\dfrac{2}{3}\)
d)
DD
28 tháng 6 2021
Mk ko ghi lại đề nhé
1 = \(350-4.19+4.7\)
\(=350-4.\left(19+7\right)\)
\(=350+4.26\)
\(=350-104=246\)
2 Câu này mình vẫn chưa hiểu là bạn ghi 27 3/5 tức là 27.3/5 hay 27\(\dfrac{3}{5}\)nên mk bỏ qua nhé
3 Cái đoạn 1 1/3 y chang câu 2 
4 \(=\dfrac{2}{3}+\dfrac{1}{3}.\dfrac{7}{18}.\dfrac{12}{7}\)
\(=\dfrac{2}{3}+\dfrac{7}{54}.\dfrac{12}{7}\)
\(=\dfrac{2}{3}+\dfrac{2}{9}=\dfrac{8}{9}\)
5 \(=2^2+10^2-\left[9.\left(112:8\right)-11\right].1\)
\(=4+100-\left(9.14-11\right)\)
\(=104-115\)\(=-11\)
6 Đoạn 6 3/5 y chang 2,3
7 \(=\left(\dfrac{2}{3}-1\right)+\left(\dfrac{2}{7}-\dfrac{3}{7}\right)-\left(\dfrac{1}{14}-\dfrac{3}{28}\right)\)
\(=\dfrac{-1}{3}+\dfrac{-1}{7}-\dfrac{-1}{28}\)
\(=\dfrac{-196}{588}+\dfrac{-84}{588}-\dfrac{-21}{588}\)\(=\dfrac{259}{588}\)
Làm tạm tạm thôi xl vì có 3 câu ko hiểu 
LL
29 tháng 6 2021
mik cách ra nghĩa là ghi 27, 3 phần 5 (mấy câu khác cx zị)hog phải nhân nha
NY
Tính giá trị biểu thức sau bằng cách hợp lí:
A= 1/2 + (-1/7) - (-1/13) +-1/13 - (-2/5) + -11/21 +1/10
1
9 tháng 6 2019
\(A=\frac{1}{2}+\frac{-1}{7}-\frac{-1}{13}+\frac{-1}{13}-\frac{-2}{5}+\frac{-11}{21}+\frac{1}{10}\)
\(A=\frac{5}{10}-\frac{3}{21}+\frac{1}{13}-\frac{1}{13}+\frac{4}{10}-\frac{11}{21}+\frac{1}{10}\)
\(A=\left(\frac{5+4+1}{10}\right)+\left(\frac{-3}{21}-\frac{11}{21}\right)+\left(\frac{1}{13}-\frac{1}{13}\right)\)
\(A=1+\frac{-2}{3}=\frac{3-2}{3}=\frac{1}{3}\)
25 tháng 2 2022
\(A=\dfrac{5}{11}.\dfrac{5}{7}+\dfrac{5}{11}.\dfrac{2}{7}+\dfrac{6}{11}=\dfrac{5}{11}\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{6}{11}=\dfrac{5}{11}.1+\dfrac{6}{11}=\dfrac{5}{11}+\dfrac{6}{11}=\dfrac{11}{11}=1\)
\(B=\dfrac{3}{13}.\dfrac{6}{11}+\dfrac{3}{13}.\dfrac{9}{11}-\dfrac{3}{13}.\dfrac{4}{11}=\dfrac{3}{13}\left(\dfrac{6}{11}+\dfrac{9}{11}-\dfrac{4}{11}\right)=\dfrac{3}{13}.1=\dfrac{3}{13}\)
\(C=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right)\left(\dfrac{3}{6}-\dfrac{2}{6}-\dfrac{1}{6}\right)=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right).0=0\)
NT
0
TD
16 tháng 2 2022
a)P=\(\dfrac{-2}{7}+\dfrac{14}{29}+\dfrac{12}{33}+\dfrac{15}{29}+\dfrac{21}{33}+\dfrac{2}{7}\)
=\(\left(\dfrac{-2}{7}+\dfrac{2}{7}\right)+\left(\dfrac{14}{29}+\dfrac{15}{29}\right)+\left(\dfrac{12}{33}+\dfrac{21}{33}\right)\)
=0+1+1=2
b)\(\dfrac{2}{7}.\dfrac{5}{19}+\dfrac{2}{7}.\dfrac{14}{19}+\dfrac{21}{19}-\dfrac{2}{7}.\dfrac{1}{5}\)
=\(\dfrac{2}{7}.\left(\dfrac{5}{19}+\dfrac{14}{19}-\dfrac{1}{5}\right)+\dfrac{21}{19}\)
=\(\dfrac{2}{7}.\dfrac{4}{5}+\dfrac{21}{19}=\dfrac{887}{665}\)
S
10 tháng 3 2023
\(\dfrac{4}{5}\)+\(\dfrac{-5}{4}\)=\(\dfrac{0}{4}\)
\(\dfrac{-1}{3}\)+\(\dfrac{2}{5}-\dfrac{5}{6}\)=\(\dfrac{-10}{30}+\dfrac{12}{30}-\dfrac{25}{30}\)=\(\dfrac{-23}{30}\)
\(\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}\)=\(\dfrac{2}{3}-\dfrac{2}{5}\)=\(\dfrac{10}{15}-\dfrac{6}{15}\)=\(\dfrac{4}{15}\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
20 tháng 7 2023
( \(\dfrac{1}{2}\) - \(\dfrac{13}{14}\)): \(\dfrac{5}{7}\) - (- \(\dfrac{2}{21}\) + \(\dfrac{1}{7}\)) : \(\dfrac{5}{7}\)
(\(\dfrac{7}{14}\) - \(\dfrac{13}{14}\)): \(\dfrac{5}{7}\) - ( - \(\dfrac{2}{21}\) + \(\dfrac{3}{21}\)): \(\dfrac{5}{7}\)
- \(\dfrac{6}{14}\): \(\dfrac{5}{7}\) - \(\dfrac{1}{21}\): \(\dfrac{5}{7}\)
= - (\(\dfrac{3}{7}\) + \(\dfrac{1}{21}\)): \(\dfrac{5}{7}\)
= -\(\dfrac{10}{21}\): \(\dfrac{5}{7}\)
= - \(\dfrac{2}{3}\)
=(7/14- 13/14):5/7-(-2/21+3/21):5/7
=-6/14* 7/5 -1/21*7/5
=(-6/14-1/21)*7/5
=-10/21*7/5
=-2/3
MÌNH CHẮC CHẮN VỚI BẠN LUÔN!!!!
\(\left(\frac{1}{2}-\frac{13}{14}\right):\frac{5}{7}-\left(-\frac{2}{21}+\frac{1}{7}:\frac{5}{7}\right)\)
\(=\left(\frac{7}{14}-\frac{13}{14}\right):\frac{5}{7}-\left(-\frac{2}{21}+\frac{3}{21}\right):\frac{5}{7}\)
\(=-\frac{6}{14}\times\frac{7}{5}-\frac{1}{21}\times\frac{7}{5}\)
\(=\left(-\frac{6}{14}-\frac{1}{21}\right)\times\frac{7}{5}\)
\(=-\frac{10}{21}\times\frac{7}{5}\)
\(=-\frac{2}{3}\)
\("k\)\(nha"\)