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a) \(\dfrac{-5}{9}-\dfrac{4}{15}+\dfrac{2}{9}-\dfrac{11}{15}\)
\(=\left(\dfrac{-5}{9}+\dfrac{2}{9}\right)-\left(\dfrac{4}{15}+\dfrac{11}{15}\right)\)
\(=\dfrac{-3}{9}-\dfrac{15}{15}\)
\(=-\dfrac{1}{3}-1\)
\(=-\dfrac{4}{3}\)
b) \(\dfrac{-8}{13}-\dfrac{7}{16}+\dfrac{21}{13}-\dfrac{1}{6}\)
\(=\left(\dfrac{-8}{13}+\dfrac{21}{13}\right)-\dfrac{7}{16}-\dfrac{1}{6}\)
\(=\dfrac{13}{13}-\dfrac{29}{48}\)
\(=1-\dfrac{29}{48}\)
\(=\dfrac{19}{48}\)
c) \(\dfrac{-15}{25}-\dfrac{14}{21}+\dfrac{8}{5}-\dfrac{5}{3}\)
\(=\dfrac{-3}{5}-\dfrac{2}{3}+\dfrac{8}{5}-\dfrac{5}{3}\)
\(=\left(\dfrac{-3}{5}+\dfrac{8}{5}\right)-\left(\dfrac{2}{3}+\dfrac{5}{3}\right)\)
\(=\dfrac{5}{5}-\dfrac{7}{3}\)
\(=1-\dfrac{7}{3}\)
\(=-\dfrac{4}{3}\)
a: =-5/9+2/9-11/15-4/15
=-3/9-1
=-12/9=-4/3
b: =-8/13+21/13-7/16-1/6
=1-1/6-7/16
=5/6-7/16
=19/48
c: =-15/25+8/5-2/3-5/3
=-7/3+1
=-4/3
a) \(\dfrac{3}{7}-\dfrac{4}{11}-\dfrac{3}{7}\)
=\(\left(\dfrac{3}{7}-\dfrac{3}{7}\right)-\dfrac{4}{11}\)
\(=-\dfrac{4}{11}\)
b) \(-\dfrac{5}{11}+\dfrac{3}{8}-\dfrac{6}{11}\)
\(=\left(-\dfrac{5}{11}-\dfrac{6}{11}\right)+\dfrac{3}{8}\)
\(=-1+\dfrac{3}{8}=-\dfrac{8}{8}+\dfrac{3}{8}=-\dfrac{5}{8}\)
c) \(\dfrac{3}{4}-\dfrac{1}{3}-\dfrac{11}{4}\)
\(=\left(\dfrac{3}{4}-\dfrac{11}{4}\right)-\dfrac{1}{3}\)
\(=-2-\dfrac{1}{3}=-\dfrac{6}{3}-\dfrac{1}{3}=-\dfrac{7}{3}\)
a: \(=\dfrac{17}{7}+\dfrac{2}{9}-\dfrac{10}{7}-\dfrac{5}{3}\cdot9=1+\dfrac{2}{9}-15=-14+\dfrac{2}{9}=-\dfrac{126}{9}+\dfrac{2}{9}=-\dfrac{124}{9}\)
b: \(=\dfrac{-11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)
c: \(=\left(\dfrac{377}{-231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot\dfrac{4-3-1}{24}=0\)
d: \(=\dfrac{12}{7}\left(19+\dfrac{5}{8}-15-\dfrac{1}{4}\right)=\dfrac{12}{7}\cdot\dfrac{35}{8}=\dfrac{15}{2}\)
a) 5+8+11+14+...+38+41.(13 số hạng )
=(5+41)+(8+38)+(11+35)...+(20+26)+23(6 cặp )
=46+46+46+...+46+23
=46x6+23=276+23=299
b)5219+6998
=12217
c)4996+2314+1003
=(4996+2314)+1003
=7310+1003=8313
a: \(19\cdot35+55\cdot81+19\cdot20\)
\(=19\cdot55+55\cdot81\)
\(=55\cdot100=5500\)
b: \(117\cdot98-117\cdot46-52\cdot17\)
\(=117\cdot52-52\cdot17\)
=5200
c: Số số hạng là:
\(\left(50-2\right):2+1=48:2+1=25\left(số\right)\)
Tổng là:
\(\dfrac{\left(50+2\right)\cdot25}{2}=\dfrac{52\cdot25}{2}=650\)
d: Số số hạng là:
50-11+1=40(số)
Tổng là:
\(\dfrac{\left(50+11\right)\cdot40}{2}=61\cdot20=1220\)
\(a,12.\dfrac{-7}{11}.\dfrac{5}{6}.\dfrac{22}{7}=\left(12.\dfrac{5}{6}\right)\left(\dfrac{-7}{11}.\dfrac{22}{7}\right)=10.\left(-2\right)=-20\\ b,\dfrac{-8}{15}.\dfrac{7}{9}.\dfrac{5}{8}.\left(-18\right)=\left(\dfrac{-8}{15}.\dfrac{5}{8}\right)\left[\dfrac{7}{9}.\left(-18\right)\right]=\dfrac{-1}{3}.\left(-14\right)=\dfrac{14}{3}\)
a) 12.−711.56.227= (12.56)(−711.227)= 10.(−2)= −20.
b) −815.79.58.(−18)= (−815.58)[79.(−18)]= −13.(−14)= 143.
a) Bạn xem lại thừa số thứ 2. Mình nghĩ phải là 149 x 327327 - 149149x327
b) Số số hạng là (2072 - 5) : 3 + 1 = 690 (số)
Tổng là (2072 + 5). 690 : 2 = 716565
a) Câu a hình như sai đề
b) Số lượng số hạng của tổng trên là :
\(\left(2072-5\right):3+1=690\) ( số )
Tổng có giá trị là :
\(\frac{\left(2072+5\right)\times690}{2}=716565\)
Đáp số : \(716565\)