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5 tháng 9 2020
Bài 1 :
\(a,\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-1\frac{7}{21}+2\)
\(=\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}-1\frac{7}{21}\right)+2\)
\(=1-1+2\)
\(=2\)
Học tốt
5 tháng 10 2022
Câu 1:
\(=\dfrac{15}{34}+\dfrac{19}{34}-1-\dfrac{15}{17}+\dfrac{1}{3}+\dfrac{3}{5}\)
\(=-\dfrac{15}{17}+\dfrac{14}{15}=\dfrac{13}{255}\)
Câu 2:
\(=\dfrac{5^4\cdot5^4\cdot2^8}{4^4\cdot6^4\cdot3^2\cdot5}=\dfrac{5^7}{6^4\cdot3^2}\)
M
23 tháng 9 2018
a, \(\dfrac{15}{34}+\dfrac{7}{21}+\dfrac{19}{34}-\dfrac{20}{15}+\dfrac{3}{7}\)
= \(\left(\dfrac{15}{34}+\dfrac{19}{34}\right)+\left(\dfrac{7}{21}+\dfrac{3}{7}\right)-\dfrac{20}{15}\)
= 1 + \(\dfrac{16}{21}-\dfrac{20}{15}\)
= \(\dfrac{3}{7}\)
b, \(\dfrac{27}{25}+\dfrac{4}{21}-\dfrac{2}{25}+\dfrac{17}{21}-\dfrac{1}{2}\)
= \(\left[\dfrac{27}{25}+\left(-\dfrac{2}{25}\right)\right]+\left(\dfrac{4}{21}-\dfrac{7}{21}\right)-\dfrac{1}{2}\)
= 1 + \(\left(\dfrac{-1}{7}\right)-\dfrac{1}{2}\) = \(\dfrac{5}{14}\)
HH
3
DH
5 tháng 9 2017
a, \(\left(-\dfrac{28}{19}\right).\left(-\dfrac{38}{19}\right)=-\dfrac{28}{19}.\left(-2\right)=\dfrac{56}{19}\)
b, \(\dfrac{-21}{-16}.\left(-\dfrac{24}{7}\right)=\dfrac{21}{16}.\left(-\dfrac{24}{7}\right)=-\dfrac{9}{2}\)
c, \(\left|-\dfrac{12}{7}.\left(-\dfrac{34}{9}\right)\right|=\left|\dfrac{136}{21}\right|=\dfrac{136}{21}\)
Chúc bạn học tốt!!!
5 tháng 9 2017
a)\(-\dfrac{28}{19}.\dfrac{-38}{19}=\dfrac{-28.\left(-38\right)}{19.19}=\dfrac{56}{19}\)
b)\(\dfrac{-21}{-16}.\dfrac{-24}{7}=\dfrac{-21.\left(-24\right)}{-16.7}=\dfrac{9}{2}\)
c)\(\text{|}\dfrac{-12}{7}.\dfrac{-34}{9}\text{|}=\text{|}\dfrac{136}{21}\text{|}=\dfrac{136}{21}\)
25 tháng 10 2018
Thực hiện phép tính bằng cách tính hợp lí
a)\(\dfrac{15}{34}+\dfrac{7}{21}+\dfrac{19}{34}-1\dfrac{15}{17}+\dfrac{2}{3}=\)
=\(\dfrac{15}{34}+\dfrac{1}{3}+\dfrac{19}{34}-1\dfrac{15}{17}+\dfrac{2}{3}\)
=\(\left(\dfrac{15}{34}+\dfrac{19}{34}\right)+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)-1\dfrac{15}{17}\)
=\(1+1-\dfrac{32}{17}\)
=\(\dfrac{34}{17}-\dfrac{32}{17}\)
=\(\dfrac{2}{17}\)
b)\(\left(-2\right)^3\cdot\left(\dfrac{3}{4}-0,25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)
=\(-8\cdot\left(\dfrac{3}{4}-\dfrac{1}{4}\right):\left(\dfrac{9}{4}-\dfrac{7}{6}\right)\)
=\(-8\cdot\dfrac{1}{2}:\left(\dfrac{54}{24}-\dfrac{28}{24}\right)\)
=\(-4:\dfrac{13}{12}\)
=\(-4\cdot\dfrac{12}{13}\)
=\(-\dfrac{48}{13}\)
\(24\cdot(34-19)-34\cdot(24-19)\)
\(=24\cdot34-24\cdot19-34\cdot24-34\cdot19\)
\(=(24\cdot34-34\cdot24)-(24\cdot19-34\cdot19)\)
\(=0-(-190)=190\)
Cách 1 :24.(34-19)-34.(24-19) =24.15-34.5
=360-170
=190
Cách 2 :24.(34-19)-34.(24-19) =24.34-24.19-34.24+34.19
=816-456-816+646
=360-816+646
=-456+646
=190