cho :
\(\dfrac{\dfrac{2}{3}n+\dfrac{1}{5}\cdot\dfrac{3}{7}+\dfrac{1}{7}\cdot\dfrac{3}{10}+\dfrac{1}{3}n-\dfrac{1}{14}+\dfrac{33}{35}}{\dfrac{2}{3}\cdot\left(3n+\dfrac{3}{5}\right)\dfrac{14}{15}+\dfrac{1}{3}}\)
a, Hãy rút gọn A.
b,Tìm giá trị của A khi n =\(\dfrac{-1}{5}\)
c,Tìm n để A nhận giá trị là \(\dfrac{2}{5}\)
d,Tìm n để 2A thuộc Z
tính tổng
S=\(\dfrac{1}{1\cdot2\cdot3}+\dfrac{1}{2\cdot3\cdot4}+\dfrac{1}{3\cdot4\cdot5}+...+\dfrac{1}{n\cdot\left(n+1\right)\cdot\left(n+2\right)}\)
A=1+\(\dfrac{1}{3}+\dfrac{1}{5}+\dfrac{1}{7}+...+\dfrac{1}{99}\)
B= \(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...\dfrac{1}{100}\)
C=\(\dfrac{99}{1}+\dfrac{98}{2}+\dfrac{97}{3}+...+\dfrac{1}{99}\)
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!
Giúp mk với mk cần lắm! AI nhanh mk tick cho! Hứa và đảm bảo!
Cảm ơn các bn trước nhé!
\(\dfrac{-5}{9}+1\dfrac{5}{9}\cdot\left(\dfrac{3}{4}-\dfrac{2}{5}\right):7^2\)
\(1\dfrac{13}{15}\cdot0,75-\left(\dfrac{104}{195}+25\%\right)\cdot\dfrac{24}{47}-3\dfrac{12}{13}:3\)
\(1\dfrac{13}{15}\cdot\left(0,5\right)^2\cdot3+\left(\dfrac{8}{15}+1\dfrac{19}{60}\right):1\dfrac{23}{24}\)
1)tìm x
a)\(\dfrac{2}{3}x+\dfrac{5}{7}=\dfrac{3}{10}\) b)\(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\) c)\(2\cdot\left(2x-\dfrac{1}{7}\right)=0\) d)\(\left(3-2x\right)\left(7x-\dfrac{1}{8}\right)=0\)
2)xác định giá trị của để:
a)\(\dfrac{x+3}{x-5}\)có giá trị âm b)\(\left(x+\dfrac{2}{3}\right)\cdot\left(x-2\right)>0\)
giúp mình !
Bài 1:Tính
a, A=\(\dfrac{3}{4}\cdot\dfrac{8}{9}\cdot\dfrac{15}{16}\cdot....\cdot\dfrac{9999}{10000}\)
b,B=\(\left(1-\dfrac{1}{21}\right)\cdot\left(1-\dfrac{1}{28}\right)\cdot\left(1-\dfrac{1}{36}\right)\cdot....\cdot\left(1-\dfrac{1}{1326}\right)\)
c,C=\(\left(1+\dfrac{1}{1\cdot3}\right)\cdot\left(1+\dfrac{1}{2\cdot4}\right)\cdot\left(1+\dfrac{1}{3\cdot5}\right)\cdot....\cdot\left(1+\dfrac{1}{99\cdot101}\right)\)
Làm đúng nhận tick!
1. Tính hợp lý giá trị các biểu thức sau:
A= \(49\dfrac{8}{23}\)\(-\left(5\dfrac{7}{32}+14\dfrac{8}{23}\right)\)
B= \(6\dfrac{3}{8}+5\dfrac{1}{2}\)
C= \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)
2. Tìm x, biết
a) \(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)
b) \(x:4\dfrac{1}{3}=-2,5\)
c) \(x:\dfrac{-3}{5}=\dfrac{-10}{21}\)
d) \(\dfrac{2}{3}.x-\dfrac{1}{2}=\dfrac{1}{10}\)
e) \(\dfrac{1}{2}.x+\dfrac{1}{2}=\dfrac{5}{2}\)
g) \(\dfrac{-2}{3}-\dfrac{1}{3}.\left(2.x-5\right)=\dfrac{3}{2}\)
h) \(\dfrac{2}{5}.x+\dfrac{1}{2}=\dfrac{-3}{4}\)
i) \(\left(2.x-2\dfrac{4}{5}\right):3\dfrac{1}{8}=1\dfrac{3}{5}\)
k) \(3,2x-\left(\dfrac{4}{5}+\dfrac{2}{3}\right):3\dfrac{2}{3}=\dfrac{7}{20}\)
j) \(\dfrac{2}{3}.x-\dfrac{3}{7}.\left(1-x\right)=\dfrac{20}{7}\)
Làm đúng nhận tick như đã nói! Hãy thể hiện trí thông minh và yêu thích bộ môn toán của mình
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: 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=\(10101.\left(\dfrac{5}{111111}+\dfrac{5}{222222}-\dfrac{4}{3.7.11.13.37}\right)\)
a)\(\dfrac{2}{7}+\dfrac{-3}{8}+\dfrac{11}{7}+\dfrac{1}{7}_{ }+\dfrac{5}{-8}\)
b)\(\dfrac{3}{17}+\dfrac{-5}{13}+\dfrac{-18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}_{ }+\dfrac{-8}{13}\)
c)\(\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{5}{-8}+\dfrac{2}{-5}+\dfrac{13}{25}\)
d)\(\dfrac{-5}{21}+\left(\dfrac{-16}{21}+1\right)\)
e)\(\dfrac{-3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)\)
f)\(\left(\dfrac{-1}{6}+\dfrac{5}{-12}\right)+\dfrac{7}{12}\)
