a: Số nghịch đảo là -1/2; 15;-27;0,5;1,2 lần lượt là -2;1/15; -1/27; 2; 5/6
b: 2/3-5/6=-1/6
1/4x5/7+1/4x(-2/7)=1/4x3/7=3/28
SỐ nghịch đảo lần lượt là -6 và 28/3
tính:
a) \(25\%-\dfrac{5}{4}+1\dfrac{5}{6}\)
b) \(75\%:2\dfrac{1}{5}-\left(0,5\right)^2.\left(-7\right)+2,5\left(7\dfrac{2}{3}-5\dfrac{2}{3}\right)\)
c) \(45:2\dfrac{4}{7}+50\%-1,25\)
d) \(350\%:\dfrac{105}{24}+4\dfrac{5}{6}:2-\left(0,5\right)^2.30\%\)
e) \(4\dfrac{2}{5}.0,5-1\dfrac{3}{7}.14\%+\left(-0,8\right)\)
Bài 1: Thực hiện phép tính
a) \(\left(\dfrac{3}{8}+\dfrac{-3}{4}+\dfrac{7}{12}\right):\dfrac{5}{6}+\dfrac{1}{2}\)
b) \(\dfrac{1}{2}+\dfrac{3}{4}-\left(\dfrac{3}{4}-\dfrac{4}{5}\right)\)
c) \(6\dfrac{5}{12}:2\dfrac{3}{4}+11\dfrac{1}{4}.\left(\dfrac{1}{3}\dfrac{1}{5}\right)\)
d)\(\left(\dfrac{7}{8}-\dfrac{3}{4}\right).1\dfrac{1}{3}-\dfrac{2}{7}.\left(3,5\right)^2\)
e)\(\left(\dfrac{3}{5}+0,415-\dfrac{3}{200}\right).2\dfrac{2}{3}.0,25\)
f)\(\dfrac{5}{16}:0,125-\left(2\dfrac{1}{4}-0,6\right).\dfrac{10}{11}\)
g) \(0,25:\left(10,3-9,8\right)-\dfrac{3}{4}\)
h)\(1\dfrac{13}{15}.0,75-\left(\dfrac{11}{20}+20\%\right):\dfrac{7}{3}\)
i)\(\dfrac{\left(\dfrac{1}{2-0,75}\right).\left(0,2-\dfrac{2}{5}\right)}{\dfrac{5}{9}-1\dfrac{1}{12}}\)
k)\(\dfrac{\dfrac{2}{3}+\dfrac{2}{7}-\dfrac{1}{14}}{-1-\dfrac{3}{7}+\dfrac{3}{28}}\)
Bài 2: Tính bằng cánh hợp lí
A=\(0,7.2\dfrac{2}{3}.20.0,375.\dfrac{5}{28}\)
B=\(\left(9\dfrac{30303}{80808}+7\dfrac{303030}{484848}\right)+4,03\)
C=\(\left(9,75.21\dfrac{3}{7}+\dfrac{39}{4}.18\dfrac{4}{7}\right).\dfrac{15}{78}\)
D=\(10101.\left(\dfrac{5}{111111}+\dfrac{5}{222222}-\dfrac{4}{3.7.11.13.37}\right)\)
tính:
a) \(2\dfrac{3}{4}.\left(-0,4\right)-1\dfrac{3}{5}.2,75+\left(-1,2\right):\dfrac{4}{11}\)
b) \(1,4.\dfrac{15}{49}-\left(\dfrac{4}{5}+\dfrac{2}{3}\right):2\dfrac{1}{5}\)
c) \(\left(-3,2\right).\dfrac{15}{64}+\left(0,8-2\dfrac{4}{15}\right):3\dfrac{2}{3}\)
d) \(0,02.\dfrac{-25}{2}+\dfrac{3}{8}+\left(-2\dfrac{9}{20}\right).\dfrac{2}{7}\)
e) \(34\%:\dfrac{51}{16}-3\dfrac{7}{9}.6,5-\left(0,4\right)^2\)
Giúp mình với 
1. Thực hiện phép tính (Tính nhanh nếu có thể):
a) \(\left(\dfrac{3}{8}+\dfrac{-4}{3}+\dfrac{7}{12}\right)\div\dfrac{5}{6}+\dfrac{1}{2}\)
b) \(0,5\times11\dfrac{1}{3}\times75\%\div\dfrac{2}{5}+\dfrac{3}{5}\)
c) \(-5^2-4\dfrac{1}{2}\left(10,6-1\dfrac{3}{5}\right)+75\%\)
d) \(\left(-3,2\right)\times\dfrac{-15}{64}+\left(0,8-2\dfrac{4}{15}\right)\div3\dfrac{2}{3}\)
e) \(\dfrac{-3}{5}\times\dfrac{2}{7}+\dfrac{-3}{5}\times\dfrac{5}{7}+2\dfrac{3}{5}\)
Bài 1; Tính
a)\(\left(\dfrac{5}{18}-\dfrac{7}{24}+\dfrac{1}{9}\right):\dfrac{7}{18}\)
b)\(\left(\dfrac{7}{20}-\dfrac{5}{16}+\dfrac{3}{40}\right):\left(\dfrac{4}{15}-\dfrac{3}{10}+\dfrac{1}{12}\right)\)
Bài 2:Tìm x
a)\(\dfrac{3}{10}-x=\dfrac{5}{6}-\dfrac{2}{15}\)
b)\(\dfrac{-5}{8}+x=\dfrac{4}{9}-\dfrac{7}{1}\)
c)\(\dfrac{2}{x-3}=\dfrac{x-3}{18}\)
Giúp mk zới m.n mk gấp lắm mk tick cho
Cho A=\(\dfrac{\dfrac{-5}{8}x\dfrac{3}{7}+\dfrac{3}{7}x\dfrac{3}{4}+\dfrac{1}{7}x\dfrac{1}{2}+\dfrac{15}{8}}{a+\dfrac{5}{6}-\left(\dfrac{-1}{3}\right)}\)
a) Rút gọn A?
b) Tính A khi a=75%
c) Tìm a để A=50%
d) Tìm a thuộc Z để A là số nguyên.
e) Với a= bao nhiêu để A có giá trị bằng với giá trj của biểu thức:
B=\(\dfrac{\dfrac{2}{3}x\dfrac{15}{6}+\left(-0,5\right)^3}{\dfrac{1}{9}x\left(6\right)^2-5\dfrac{1}{3}}\)
Dấu x là dấu nhân nhé!
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Cảm ơn các bn trước nhé!
Tính rồi tìm số nghịch đảo của :
\(\dfrac{2}{3}.\dfrac{4}{5}.\dfrac{6}{7}.\dfrac{8}{9}.\dfrac{10}{11}.\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}.\dfrac{7}{8}.\dfrac{9}{10}\)
tính nhanh :
a) \(6\dfrac{5}{7}-\left(1\dfrac{3}{4}+2\dfrac{5}{7}\right)\)
b) \(7\dfrac{5}{11}-\left(2\dfrac{3}{7}+3\dfrac{5}{11}\right)\)
c) \(\dfrac{1}{3}.\dfrac{4}{5}+\dfrac{1}{3}.\dfrac{6}{5}-\dfrac{4}{3}\)
d) \(\left(\dfrac{-4}{5}+\dfrac{4}{3}\right)+\left(\dfrac{-5}{4}+\dfrac{14}{5}\right)-\dfrac{7}{3}\)
e) \(\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{14}+1\dfrac{5}{7}\)
Bài 1: Tìm x, biết:
a, \(\left(x+\dfrac{1}{4}-\dfrac{1}{3}\right):\left(2+\dfrac{1}{6}-\dfrac{1}{4}\right)=\dfrac{7}{46}\)
b, \(\dfrac{13}{15}-\left(\dfrac{13}{21}+x\right).\dfrac{7}{12}=\dfrac{7}{10}\)
Bài 2: Thực hiện phép tính:
a, \(\left(2\dfrac{5}{6}+1\dfrac{4}{9}\right):\left(10\dfrac{1}{12}-9\dfrac{1}{2}\right)\)
b, 1\(\dfrac{5}{18}-\dfrac{5}{18}.\left(\dfrac{1}{15}+1\dfrac{1}{12}\right)\)
c, \(-\dfrac{1}{7}.\left(9\dfrac{1}{2}-8,75\right):\dfrac{2}{7}+0,625:1\dfrac{2}{3}\)
