(-12 . 2/7 + 8/9 : 7/2 - 2/7 . 5/18 ) . 7/2
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1: =72/90+65/90=137/90
2: =24/56-77/56=-53/56
3: =-7/10+4/5=1/10
4: =15/100-4/100=11/100
5: =4/6-5/6=-1/6
6: =10/40-15/40-76/40=-81/40
7: =-9/10+7/18
=-81/90+35/90=-46/90=-23/45
8: =27/90-55/90=-28/90=-14/45
9: =36/60-50/60-35/60=-49/60
10: =-4/9+5/6-3/8
=-32/72+60/72-27/72
=1/72
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5/-6+-5/12 +7/18 = -31/36
2/9+-3/10+-7/10 = 2/9+(-3/10+-7/10)=2/9+(-1)=7/9
-11/6 +2/5 +-1/6 =2/5 +(-11/6+-1/6)=2/5 + -2 =-8/5
-5/8+12/7+13/8+2/7 =(-5/8+13/8)+(12/7+2/7)=1+2=3
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a: =7/8:(2/9-18+1/36)-5/12
=-7/142-5/12=-397/852
b: =3/7(4/9+5/9:6/12)=2/3
c: =5^8(16/31-47/31)+1/3=-5^8+1/3
d: =7/2(3/8+5/8:4/15)=609/64
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\(\dfrac{8}{9}+\dfrac{3}{18}=\dfrac{16}{18}+\dfrac{3}{18}=\dfrac{19}{18}\) \(\dfrac{5}{7}-\dfrac{4}{11}=\dfrac{55}{77}-\dfrac{28}{77}=\dfrac{3}{11}\)
\(\dfrac{3}{4}+\dfrac{4}{5}=\dfrac{15}{20}+\dfrac{16}{20}=\dfrac{21}{20}\) \(\dfrac{5}{7}-\dfrac{3}{5}=\dfrac{25}{35}-\dfrac{21}{35}=\dfrac{4}{35}\)
\(\dfrac{7}{9}X\dfrac{3}{4}=\dfrac{7}{9}X\dfrac{3}{4}=\dfrac{7}{12}\) \(\dfrac{8}{3}X\dfrac{21}{4}=\dfrac{8}{3}X\dfrac{21}{4}=14\)
\(\dfrac{12}{7}:\dfrac{1}{4}=\dfrac{12}{7}X\dfrac{4}{1}=\dfrac{48}{7}\) \(\dfrac{7}{2}:\dfrac{9}{4}=\dfrac{7}{2}X\dfrac{4}{9}=\dfrac{14}{9}\)
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Ta có: 7/8 : (2/9 - 1/8) + 7/8 : (1/30 - 5/12) = 7/8 : 7/72 + 7/8 : (-23/60)
= 7/8.(72/7 - 60/23)
= 7/8 . 1236/161 = 309/46
\(\left(-12.\frac{2}{7}+\frac{8}{9}:\frac{7}{2}-\frac{2}{7}.\frac{5}{18}\right).\frac{7}{2}\)
\(=\left(-12.\frac{2}{7}+\frac{8}{9}.\frac{2}{7}-\frac{2}{7}.\frac{5}{18}\right).\frac{7}{2}\)
\(=\left[\frac{2}{7}.\left(-12+\frac{8}{9}-\frac{5}{18}\right)\right].\frac{7}{2}\)
\(=\left(\frac{2}{7}.-\frac{205}{18}\right).\frac{7}{2}\)
\(=\left(\frac{2}{7}.\frac{7}{2}\right).-\frac{205}{18}\)
\(=1.\left(-\frac{205}{18}\right)\)
\(=\left(-\frac{205}{18}\right)\)