Tính hợp lí: a)15/34-8/21+19/34-34/21
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5 tháng 12 2018
(34 - 53 + 28) - (34 - 53 - 21)
= 34 - 53 + 38 - 34 + 53 + 21
= (34 - 34) - (53 - 53) + (38 + 21)
= 0 - 0 + 59
= 59
9 tháng 8 2019
\(a,\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{20}{15}+\frac{3}{7}\)
\(=>\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}+\frac{3}{7}\right)-\frac{20}{15}\)
\(=>1+\frac{16}{21}-\frac{20}{15}\)
\(=>\frac{37}{21}-\frac{20}{15}\)
\(=>\frac{3}{7}\)
\(b,12-8\cdot\left(\frac{3}{2}\right)^3\)
\(=>12-8\cdot\frac{27}{8}\)
\(=>12-27\)
\(=>-15\)
\(c,\left(\frac{1}{9}\right)^{2005}\cdot9^{2005}-96^2:24^2\)
\(=>\left(\frac{1^{2005}^{ }}{9^{2005}}\cdot9^{2005}\right)-\left(96^2:24^2\right)\)
\(=>\left(1^{2005}\right)-16\)
\(=>1-16\)
\(=>-15\)
ND
Nguyễn Đức Trí
VIP
24 tháng 8 2023
a) \(...=-\dfrac{12}{46}-\dfrac{15}{21}+\dfrac{3}{7}-\dfrac{7}{23}\)
\(=-\dfrac{12}{46}-\dfrac{7}{23}-\dfrac{15}{21}+\dfrac{3}{7}\)
\(=-\dfrac{6}{23}-\dfrac{7}{23}-\dfrac{5}{7}+\dfrac{3}{7}\)
\(=-\dfrac{13}{23}-\dfrac{2}{7}\)
\(=-\dfrac{13.7}{23.7}-\dfrac{2.23}{23.7}\)
\(=-\dfrac{91}{161}-\dfrac{46}{161}=-\dfrac{137}{161}\)
b) \(...=-21+\dfrac{7}{9}-\dfrac{3}{17}+\dfrac{25}{9}\)
\(=-21-\dfrac{3}{17}+\dfrac{7}{9}+\dfrac{25}{9}\)
\(=-21-\dfrac{3}{17}+\dfrac{32}{9}\)
\(=-\dfrac{3213}{153}-\dfrac{27}{153}+\dfrac{544}{153}=-\dfrac{2696}{153}\)
DX
26 tháng 7 2021
\(\dfrac{15}{34}+\dfrac{7}{21}+\dfrac{19}{34}-\dfrac{32}{17}+\dfrac{2}{3}\)
\(=\left(\dfrac{15}{34}+\dfrac{19}{34}\right)+\dfrac{7}{21}+\dfrac{-32}{17}+\dfrac{2}{3}\)
\(=1+\dfrac{1}{3}+\dfrac{-32}{17}+\dfrac{2}{3}\)
\(=1+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)+\dfrac{-32}{17}\)
\(=1+1+\dfrac{-32}{17}\)
\(2+\dfrac{-32}{17}=\dfrac{2}{17}\)
a)15/34-8/21+19/34-34/21
=(15/34+19/34)+(-8/21-34/21)
= 34/34+(-42/21)
=1+(-2)
=-1
đề tự ghi lại nha
=\(\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{-8}{21}-\frac{34}{21}\right)\)
=\(\frac{34}{34}+\frac{-42}{21}\)
=\(1+\left(-2\right)\)
=\(-1\)