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Câu a:
7/10.4/9 + 3/10.4/9 - 1 7/9
= 4/9.(7/10 + 3/10) - 16/9
= 4/9 - 16/9
= - 12/9
= - 4/3
Câu b:
- 5/6 + 4/9.(5/4 - 2/3).(-3)^2 + 5/9.30%
= - 5/6 + [5/9 - 8/27].9 + 5/9.3/10
= - 5/6 + 5 - 8/3 + 1/6
= (-5/6 + 1/6) - 8/3 + 5
= - 4/6 - 8/3 + 15/3
= - 2/3 - 8/3 + 15/3
= - 10/3 + 15/3
= 5/3
a,\(\frac{7}{10}\cdot\frac{4}{9}+\frac{3}{10}\cdot\frac{4}{9}-1\frac{7}{9}\)
\(=\frac{14}{45}+\frac{2}{15}-\frac{16}{9}\)
\(=\frac{14}{45}+\frac{6}{45}-\frac{80}{45}\)
\(=\frac{-60}{45}=\frac{-4}{3}\)
b,\(\frac{-5}{6}+\frac{4}{9}\cdot\left(\frac{5}{4}-\frac{2}{3}\right)\cdot\left(-3\right)^2+\frac{5}{9}\cdot30\%\)
\(=\frac{-5}{6}+\frac{4}{9}\cdot\left(\frac{7}{12}\right)\cdot9+\frac{5}{9}\cdot\frac{3}{10}\)
\(=\frac{-5}{6}+\frac{7}{3}+\frac{1}{6}\)
\(=\frac{-5}{6}+\frac{14}{6}+\frac{1}{6}\)
=\(=\frac{10}{6}=\frac{5}{3}\)
Câu c:
1/2017.(1/3 - 7/12 + 1/4) - (6 2/3 - 1,5.2^2) :5/6
= 1/2017.(4/12 - 7/12 + 3/12) - (20/3 - 1,5x 4) : 5/6
= 1/2017.0 - (20/3 - 6) x 6/5
= 0 - (20/3 - 18/3) x 6/5
= - 2/3 x 6/5
= - 4/5
Câu a:
A = 7 2/13 - (5 2/13 + 2 1/2)
A = 7 2/13 - 5 2/13 - 2 1/2
A = 2 - 2 1/2
A = 2 - 2 - 1/2
A = 0 - 1/2
A = -1/2
Câu b:
B = - 3/4 + 25% : (10 3/10 - 9 4/5) - (-1/2)^2
B = - 3/4 + 1/4 : (103/10 - 49/5) - 1/4
B = - 3/4 + 1/4 : (103/10 - 98/5) - 1/4
B = (-3/4 - 1/4) + 1/4 : (1/2)
B = -1 + 1/4 x 2/1
B = -1 + 1/2
B = - 1/2
Câu a:
A = 7 2/13 - (5 2/13 + 2 1/2)
A = 7 2/13 - 5 2/13 - 2 1/2
A = 2 - 2 1/2
A = 2 - 2 - 1/2
A = 0 - 1/2
A = -1/2
Câu b:
B = - 3/4 + 25% : (10 3/10 - 9 4/5) - (-1/2)^2
B = - 3/4 + 1/4 : (103/10 - 49/5) - 1/4
B = - 3/4 + 1/4 : (103/10 - 98/5) - 1/4
B = (-3/4 - 1/4) + 1/4 : (1/2)
B = -1 + 1/4 x 2/1
B = -1 + 1/2
B = - 1/2
a, 13/6+5/8 : -3/4 - 7/12.4
= 13/6 + -5/6-7/3
=8/6-7/3
= -6/6
= -1
b, ( 73/5 - 21/3) + ( 4/3-43/5 )
= 73/5-21/3+4/3-43/5
=( 73/5-43/5)-(21/3-4/3)
= 6-17/3
=1/3
c, 7/5.4/9 +7/5: 9/16- 14/10.2/9
= 7/5.4/9 +7/5.16/9 - 14/45
=7/5.(4/9+16/9)-14/45
=7/5.20/9-14/45
= 140/45 - 14/45
= 126/45
Xong rùi nè! Nhưng bạn kiểm tra lại giùm nhé vì làm vào ban đêm nên hơi bất tiện
Câu a )
\(-\frac{3}{5}+\frac{9}{16}+-\frac{2}{5}+\frac{7}{16}=\left(-\frac{3}{5}+-\frac{2}{5}\right)+\left(\frac{9}{16}+\frac{7}{16}\right).\)
\(=\left(-1\right)+1=0\)
hk tốt !
Bài 2:
Ta thấy: 52 > 4.5
62 > 5.6
72 > 6.7
....
20172 > 2016.2017
\(\Rightarrow\)\(\frac{1}{5^2}< \frac{1}{4.5}\)
\(\frac{1}{6^2}< \frac{1}{5.6}\)
\(\frac{1}{7^2}< \frac{1}{6.7}\)
....
\(\frac{1}{2017^2}< \frac{1}{2016.2017}\)
Cộng vế với nhau, ta có:
\(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2017^2}\) < \(\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{2016.2017}\)
\(\Rightarrow\)A < \(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{2016}-\frac{1}{2017}\)
\(\Rightarrow\)A < \(\frac{1}{4}-\frac{1}{2017}\)
\(\Rightarrow\)A < \(\frac{1}{4}\)( vì \(\frac{1}{2017}>0\))
k giúp mik ✅
Bài 1:
- 2 2/15 .3/8 - (7/20 - 75%) : 8/5
= -32/15.3/8 - (7/20 - 3/4) x 5/8
= - 4/5 - (7/20 - 15/20) x 5/8
= - 4/5 + 8/20 x 5/8
= - 4/5 + 1/4
= - 16/20 + 5/20
= - 11/20
\(\frac{4}{5}\)+ \(\frac{1}{5}\): \(\frac{-2}{15}\)= \(\frac{4}{5}\)+ \(\frac{1}{5}\)* \(\frac{-15}{2}\)=\(\frac{4}{5}\) + \(\frac{-3}{2}\)= \(\frac{-7}{10}\)
b = \(\frac{-7}{12}\). (\(\frac{3}{11}\)+ \(\frac{-14}{11}\)) + \(\frac{5}{6}\)= \(\frac{-7}{12}\). (-1) + \(\frac{5}{6}\)= \(\frac{7}{12}\)+ \(\frac{10}{12}\)= \(\frac{17}{12}\)
a)=-7/21+8/24
=-1/3+1/3
=0
b)=-3/5.(2/7+5/7)+23/5
=-3/5.7/7+23/5
=-3/5.1+23/5
=-3/5+23/5
=20/5=4
c)=75/100-11/2+5/10:5/12+1/4
=3/4-11/2+1/2:5/12+1/4
=3/4+-11/2+1/2.12/5+1/4
=3/4+-22/4+6/5+1/4
=-19/4+6/5+1/4
=(-19/4+1/4)+6/5
=-18/4+6/5
=-9/2+6/5
=-45/10+12/10
=-23/10