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Câu 1:
\(=\dfrac{21}{31}+\dfrac{1}{3}-\dfrac{44}{53}+\dfrac{10}{31}-\dfrac{9}{53}=\dfrac{1}{3}\)
Câu 2:
1: =>1,3x=-1,31
=>130x=-131
=>x=-131/130
2: =>(4,5-2x)=11/14:(-11/7)=-7/14=-1/2=-0,5
=>2x=5
=>x=5/2
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 2:
1:=>1,3x=-1,31
=>x=-131/130
2: =>\(\left(4.5-2x\right)=\dfrac{11}{14}:\dfrac{-11}{7}=\dfrac{-1}{2}=-0.5\)
=>2x=5
=>x=5/2
![](https://rs.olm.vn/images/avt/0.png?1311)
a, -3/4 + 3/7 + -1/4 + 4/9 + 4/7
=(−34+−14)+(37+47)+49(−34+−14)+(37+47)+49
=−1+1+49−1+1+49
=49
![](https://rs.olm.vn/images/avt/0.png?1311)
a, -3/4 + 3/7 + -1/4 + 4/9 + 4/7
=\(\left(\frac{-3}{4}+\frac{-1}{4}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)+\frac{4}{9}\)
=\(-1+1+\frac{4}{9}\)
=\(\frac{4}{9}\)
b, -7/9 x 4/11 + -7/9 x 7/11 + 5 và 7/9
\(=\frac{7}{9}x\frac{-4}{11}+\frac{7}{9}x\frac{-7}{11}+5x\frac{7}{9}\)
\(=\frac{7}{9}x\left(\frac{-4}{11}+\frac{-7}{11}+5\right)\)
\(=\frac{7}{9}x4\)
\(=\frac{28}{9}\)
c, ( 21/31 + 2013/6039 ) - ( 44/53 - 10/31) - /53
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\frac{21}{31}+\frac{2013}{6039}\right)-\left(\frac{44}{53}-\frac{10}{31}\right)-\frac{9}{53}\)
\(=\frac{21}{31}+\frac{1}{3}-\frac{44}{53}+\frac{10}{31}-\frac{9}{53}\)
\(=\left(\frac{21}{31}+\frac{10}{31}\right)+\left(\frac{-44}{53}-\frac{9}{53}\right)+\frac{1}{3}\)
\(=1+\left(-1\right)+\frac{1}{3}\)
\(=\frac{1}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\frac{-3}{4}+\frac{3}{7}+\frac{-1}{4}+\frac{4}{9}+\frac{4}{7}\)
\(=\frac{-3}{4}+\frac{-1}{4}+\frac{3}{7}+\frac{4}{7}+\frac{4}{9}\)
\(=-1+1+\frac{4}{9}\)
\(=\frac{4}{9}\)
\(b,\frac{-7}{9}\cdot\frac{4}{11}+\frac{-7}{9}\cdot\frac{7}{11}+5\frac{7}{9}\)
\(=\frac{-7}{9}\cdot\left(\frac{4}{11}+\frac{7}{11}\right)+\frac{52}{9}\)
\(=\frac{-7}{9}\cdot1+\frac{52}{9}\)
\(=\frac{-7}{9}+\frac{52}{9}=\frac{45}{9}=5\)
Ý c) bn tự làm nha. Mk ko làm đc. Nhìn nó rắc rối lắm.
Chúc bn hc tốt nha !!! TỨ DIỆP THẢO
![](https://rs.olm.vn/images/avt/0.png?1311)
bỏ ngoặc: 21/31+2013/6039-44/53+10/31-9/53
ta có ; (21/31+10/31)-(44/53+9/53)+1/3
1-1+1/3=1/3
(21/31+2013/6039)-(44/53-10/31)-9/53
=21/31+1/3-44/53+10/31-9/53
=(21/31+10/31)-(44/53+9/53)+1/3
=31/31-53/53+1/3
=1-1+1/3
=0+1/3
=1/3!!!
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\frac{21}{31}-\frac{10}{31}\right)-\left(\frac{44}{53}+\frac{9}{53}\right)+\frac{1}{3}\)
\(\frac{11}{31}-1+\frac{1}{3}\)
\(\frac{-29}{93}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
= 21/31 + 1/3 - 44/53 + 10/31 -9/53
= [21/31+10/31] - [44/53 + 9/53] +1/3
= 1-1+1/3 = 1/3