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a) \(\dfrac{7}{30}+\dfrac{\left(-12\right)}{37}+\dfrac{23}{30}+\dfrac{\left(-25\right)}{37}=\left(\dfrac{7}{30}+\dfrac{23}{30}\right)+\left(\dfrac{-12}{37}+\dfrac{-25}{37}\right)=1+\left(-1\right)=0\)
b) \(\dfrac{5}{7}\cdot\dfrac{5}{11}+\dfrac{5}{7}\cdot\dfrac{2}{11}-\dfrac{5}{7}\cdot\dfrac{14}{11}=\dfrac{5}{7}\cdot\left(\dfrac{5}{11}+\dfrac{2}{11}-\dfrac{14}{11}\right)=\dfrac{5}{7}\cdot\left(-\dfrac{7}{11}\right)=-\dfrac{5}{11}\)
c) \(\dfrac{\left(-5\right)}{7}\cdot\dfrac{3}{13}-\dfrac{5}{7}\cdot\dfrac{10}{13}+1\dfrac{5}{7}=\dfrac{5}{7}\cdot\dfrac{-3}{13}-\dfrac{5}{7}\cdot\dfrac{10}{13}+\dfrac{12}{7}=\dfrac{5}{7}\cdot\left(\dfrac{-3}{13}-\dfrac{10}{13}\right)+\dfrac{12}{7}=\dfrac{5}{7}\cdot\left(-1\right)+\dfrac{12}{7}=\left(-\dfrac{5}{7}\right)+\dfrac{12}{7}=\dfrac{7}{7}=1\)
#)Trả lời :
a) \(\frac{-1}{2}+\frac{2}{7}-\frac{5}{28}\)
\(=\frac{-3}{14}-\frac{5}{28}\)
\(=\frac{-11}{28}\)
b) \(5\frac{3}{4}+\left(\frac{1}{9}-1\frac{3}{4}\right)\)
\(=\left(5\frac{3}{4}-1\frac{3}{4}\right)+\frac{1}{9}\)
\(=4+\frac{1}{9}\)
\(=4\frac{1}{9}=\frac{37}{9}\)
c) \(\frac{-5}{7}x\frac{2}{11}+\frac{-5}{7}x\frac{9}{11}+3\frac{5}{7}\)
\(=\frac{-5}{7}x\left(\frac{2}{11}+\frac{9}{11}\right)+3\frac{5}{7}\)
\(=\frac{-5}{7}x1+3\frac{5}{7}\)
\(=\frac{-5}{7}+3\frac{5}{7}\)
\(=\frac{-5}{7}+\frac{26}{7}\)
\(=\frac{21}{7}=3\)
#~Will~be~Pens~#
a) 2 + 4 + 6 + ... + 100
\(=\frac{\left[\left(100-2\right):2+1\right].\left(100+2\right)}{2}=2550\)
b) 1 + 3 + 7 + ... + 99
\(=\frac{\left[\left(99-1\right):2+1\right].\left(99+1\right)}{2}=2500\)
c) 1 + 5 + 9 + 13 + ... + 49
\(=\frac{\left[\left(49-1\right):4+1\right].\left(49+1\right)}{2}=325\)
\(=\dfrac{5\left(5+2\right)}{11.7}+\dfrac{6}{11}=\dfrac{5}{11}+\dfrac{6}{11}=1\)
Ta có:
= 5/11 .( 5/7+ 2/7 ) + 6/11
= 5/11 . 1 + 6/11
= 11/ 11
= 1
#học tốt ạ :3
\(a.36+15+64\\ =\left(36+64\right)+15\\ =100+15\\ =115\\ b.12\cdot36+12\cdot64\\ =12\cdot\left(36+64\right)\\ =12\cdot100\\ =1200\\ c.\left(3^2+2^3\cdot5\right):7\\ =\left(9+8\cdot5\right):7\\ =\left(9+40\right):7\\ =49:7\\ =7\)\(\)
\(\dfrac{-5}{7}.\dfrac{2}{11}-\dfrac{5}{11}.\dfrac{9}{7}-2\dfrac{5}{7}\)
\(=\dfrac{-2}{7}.\dfrac{5}{11}-\dfrac{5}{11}.\dfrac{9}{7}-\dfrac{19}{7}\)
\(=\dfrac{5}{11}.\left(\dfrac{-2}{7}-\dfrac{9}{7}\right)-\dfrac{19}{7}\)
\(=\dfrac{5}{11}.\dfrac{-11}{7}-\dfrac{19}{7}\)
\(=\dfrac{-5}{7}-\dfrac{19}{7}\)
\(=\dfrac{-24}{7}\)
\(\dfrac{-5}{7}.\dfrac{2}{11}-\dfrac{5}{11}.\dfrac{9}{7}-2\dfrac{5}{7}\)
\(=\dfrac{-2}{7}.\dfrac{5}{11}-\dfrac{5}{11}.\dfrac{9}{7}-\dfrac{19}{7}\)
\(=\dfrac{5}{7}\left(\dfrac{-2}{7}-\dfrac{9}{7}\right)-\dfrac{19}{7}\)
\(=\dfrac{5}{7}.\dfrac{-11}{7}-\dfrac{19}{7}\)
\(=\dfrac{5.\left(-11\right)}{11.7}-\dfrac{19}{7}\)
\(=\dfrac{-5.11}{11.7}-\dfrac{19}{7}\)
\(=\dfrac{-5}{7}-\dfrac{19}{7}\)
\(=\dfrac{-5-19}{7}\)
\(=\dfrac{\left(-5\right)+\left(-19\right)}{7}\)
\(=\dfrac{-24}{7}\)