Tính (Hợp lý nếu có) :4/7:(2/5×4/7)
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19/57 . 2 4/7 - 19/57 . 1 5/7 - 19/57
= 19/57 x ( 2 4/7 - 1 5/7 )
= 19/57 x 6/7
= 2/7
\(\dfrac{19}{57}.2\dfrac{4}{7}-\dfrac{19}{57}.1\dfrac{5}{7}-\dfrac{19}{57}\)
\(\text{=}\dfrac{19}{57}.\left(2\dfrac{4}{7}-1\dfrac{5}{7}-1\right)\)
\(\text{=}\dfrac{19}{57}.\left(\dfrac{-1}{7}\right)\)
\(\text{=}\dfrac{-1}{21}\)
\(a,=\dfrac{4}{12}+\dfrac{15}{12}-\dfrac{7}{12}=\dfrac{12}{12}=1\\ b,=1,6\left(2\dfrac{1}{4}-3\dfrac{1}{2}\right)\\ =1,6\cdot\dfrac{-3}{4}=-2,4\)
\(\left(-\frac{3}{4}+\frac{59}{9}\right):\left(-\frac{7}{23}\right)+\left(\frac{5}{9}-\frac{1}{4}\right):\frac{7}{23}\)
= \(\left(-\frac{3}{4}+\frac{59}{9}\right).\left(-\frac{23}{7}\right)+\left(\frac{5}{9}-\frac{1}{4}\right).\left(\frac{23}{7}\right)\)
=\(\left(-\frac{23}{7}\right).\left(-\frac{3}{4}+\frac{59}{9}-\frac{5}{9}+\frac{1}{4}\right)\)
=\(\left(-\frac{23}{7}\right).\left(-\frac{2}{4}+\frac{54}{9}\right)=\left(-\frac{23}{7}\right).\left(-\frac{1}{4}+6\right)\)
=\(\left(-\frac{23}{7}\right).\frac{11}{2}=-\frac{253}{14}\)
\(a,-35.12-8.35\)
\(=\left(-35\right)\left(12+8\right)\)
\(=-700\)
\(b,-23.7-7.59-18.7\)
\(=7\left(-23-59-18\right)\)
\(7.\left(-100\right)=-700\)
\(b,115-\left(-12+29\right)\)
\(=115+12-29\)
\(=98\)
\(c,3.\left(-7\right)^2+5.\left(-4\right)^3\)
\(=3.49-5.64\)
\(=147-320\)
\(=-173\)
a)-35.12-8-35=-35(12+8)=-35.20=-700
b)23.(-7)-7.5+(-18).7=-7(23+59+18)=-7.100=-700
c)115-(-12+29)=115+12-29=98
d)\(3\left(-7\right)^2+5\left(-4\right)^3=3.7^2-5.4^3=3.49-5.64=147-320-173\)
c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)
\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)
\(=1-2=-1\)
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
\(=\frac{4}{7}+\frac{4}{7}-\frac{15}{28}\)
=\(\frac{4}{7}.\left(1+1-0,9375\right)\)
=\(\frac{17}{28}\approx0,61\)
\(=\dfrac{-3}{4}-\dfrac{1}{2}-\dfrac{3}{4}+\dfrac{5}{8}=\dfrac{-6}{4}+\dfrac{5}{8}-\dfrac{1}{2}=-2+\dfrac{5}{8}=\dfrac{-16+5}{8}=-\dfrac{11}{8}\)
`8 2/7-(3 4/9+4 2/7)`
`=8+2/7-(3+4/9+4+2/7)`
`=8+2/7-7-2/7-4/9`
`=1-4/9`
`=5/9`
8 2/7-(3 4/9+4 2/7)
=58/7-31/9-30/7
=(58/7-30/7)-31/9
=4-31/9
=5/9
#)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~#
4/7 : ( 2/5 x 4/7 )
=4/7 : 8/35
= 5/2
chúc bạn học tốt >.<