7/12+...........=1
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LD
21 tháng 5 2017
\(=\frac{12}{15}.\left(\frac{2}{7}+\frac{3}{7}+\frac{1}{7}+\frac{1}{7}\right)\)
\(=\frac{12}{15}.1\)
\(=\frac{12}{15}=\frac{4}{5}\)
Y
23 tháng 6 2023
\(7,\)
\(A=7+\left(\dfrac{7}{12}-\dfrac{1}{2}+3\right)-\left(\dfrac{1}{12}+5\right)\)
\(=7+\dfrac{7}{12}-\dfrac{1}{2}+3-\dfrac{1}{12}-5\)
\(=\left(\dfrac{7}{12}-\dfrac{1}{12}\right)+\left(7+3-5\right)-\dfrac{1}{2}\)
\(=\dfrac{6}{12}+5-\dfrac{1}{2}\)
\(=\left(\dfrac{1}{2}-\dfrac{1}{2}\right)+5\)
\(=5\)
\(8,\)
\(A=-\dfrac{1}{4}+\dfrac{7}{33}-\dfrac{5}{3}-\left(-\dfrac{15}{12}+\dfrac{6}{11}-\dfrac{68}{49}\right)\)
\(=-\dfrac{1}{4}+\dfrac{7}{33}-\dfrac{5}{3}+\dfrac{15}{12}-\dfrac{6}{11}+\dfrac{68}{49}\)
\(=\left(-\dfrac{1}{4}+\dfrac{15}{12}\right)+\left(\dfrac{7}{33}-\dfrac{5}{3}-\dfrac{6}{11}\right)+\dfrac{68}{49}\)
\(=\left(-\dfrac{3}{12}+\dfrac{15}{12}\right)+\left(\dfrac{7}{33}-\dfrac{55}{33}-\dfrac{18}{33}\right)+\dfrac{68}{49}\)
\(=\dfrac{12}{12}-\dfrac{66}{33}+\dfrac{68}{49}\)
\(=1-2+\dfrac{68}{49}\)
\(=-1+\dfrac{68}{49}\)
\(=\dfrac{19}{49}\)
H9
HT.Phong (9A5)
CTVHS
10 tháng 7 2023
\(-\dfrac{7}{12}\cdot\dfrac{3}{8}+-\dfrac{7}{12}\cdot\dfrac{5}{8}+1\dfrac{7}{12}\)
\(=-\dfrac{7}{12}\cdot\left(\dfrac{3}{8}+\dfrac{5}{8}-1\right)\)
\(=-\dfrac{7}{12}\cdot\left(\dfrac{8}{8}-1\right)\)
\(=-\dfrac{7}{12}\cdot\left(1-1\right)\)
\(=-\dfrac{7}{12}\cdot0\)
\(=0\)
14 tháng 2 2022
a: \(=\dfrac{-5}{8}+\dfrac{7}{12}=\dfrac{-15}{24}+\dfrac{14}{24}=\dfrac{-1}{24}\)
b: \(=\dfrac{3}{4}-\dfrac{5}{6}+\dfrac{11}{12}=\dfrac{9}{12}-\dfrac{10}{12}+\dfrac{11}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)
c: \(=\dfrac{6}{36}-\dfrac{1}{36}=\dfrac{5}{36}\)
d: \(=\dfrac{5}{12}+\dfrac{5}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)
e: \(=\dfrac{-8}{56}-\dfrac{7}{56}=\dfrac{-15}{56}\)
f: \(=\dfrac{-5}{15}+\dfrac{3}{25}=\dfrac{-25}{75}+\dfrac{9}{75}=\dfrac{-16}{75}\)
C
23 tháng 9 2018
\(\dfrac{12}{17}.\dfrac{5}{7}-\left(-\dfrac{12}{17}\right).\dfrac{1}{7}+\dfrac{1}{17+7}\)
\(=\dfrac{12}{17}.\dfrac{5}{7}+\dfrac{12}{17}.\dfrac{1}{7}+\dfrac{1}{24}\)
\(=\dfrac{12}{17}\left(\dfrac{5}{7}+\dfrac{1}{7}\right)+\dfrac{1}{24}\)
\(=\dfrac{12}{17}.\dfrac{6}{7}+\dfrac{1}{24}\)
\(=\dfrac{72}{119}+\dfrac{1}{24}=\dfrac{1847}{2856}\)
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
DH
chứng minh rằng A= 12/1*4*7+12/4*7*10+12/7*10*13+...+12/54*57*60<1/2
giải giup minh nha minh tich cho
2
17 tháng 2 2017
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9 tháng 9 2021
\(d,=24x^2-38x+3\\ e,=x^2-12x+35\\ f,=\left(x^2-144\right)\left(4x-1\right)=4x^3-x^2-576x+144\)
\(\frac{7}{12}+\frac{5}{12}=1\)