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Tính:
a, 8.( -9/12 )
b, ( -14/5 ) . (-10)
c, 9. ( 4/-3 )
d, -15. ( -5/6 )
e, 13. ( -2/7 )
f, 7/26. ( -13 )
\(a,8.\left(\dfrac{-9}{12}\right)=\dfrac{8.\left(-9\right)}{12}=\dfrac{-72}{12}=-6\\ b,\left(\dfrac{-14}{5}\right).\left(-10\right)=\dfrac{\left(-14\right).\left(-10\right)}{5}=\dfrac{140}{5}=28\\ c,9.\left(\dfrac{4}{-3}\right)=\dfrac{9.\left(-4\right)}{3}=\dfrac{-36}{3}=-12\\ d,-15.\left(\dfrac{-5}{6}\right)=\dfrac{\left(-15\right).\left(-5\right)}{6}=\dfrac{75}{6}\\ e,13.\left(\dfrac{-2}{7}\right)=\dfrac{13.\left(-2\right)}{7}=\dfrac{-26}{7}\\ f,\dfrac{7}{26}.\left(-13\right)=\dfrac{7.\left(-13\right)}{26}=\dfrac{-91}{26}\)
a, 8.( -9/12 )=-6
b, ( -14/5 ) . (-10)=28
c, 9. ( 4/-3 )=-12
d, -15. ( -5/6 )=25/2
e, 13. ( -2/7 )-36/7
f, 7/26. ( -13 )=-7/2
a)=20.(-6)+42.(-20)
=-120+(-840)=-960
b)=-15.26-26.(-24)
=-390+624=234
c)=-54.9+35.(-119)
=-486-4165=-4651
d)=25.(-72+21-49)
=25.(-100)=-2500
\(\frac{5.4^{15}.9^9-4.3^{20}.8^9}{5.2^9.6^{19}-7.2^{29}.27^6}\)
\(=\frac{5.2^{30}.3^{18}-3^{20}.2^{29}}{5.2^9.3^{19}.2^{19}-7.2^{29}.3^{18}}\)
\(=\frac{5.2^{30}.3^{18}-3^{20}.2^{29}}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)
\(=\frac{3^{18}.2^{29}.\left(5+1-9+2\right)}{2^{28}.3^{18}.\left(5+3-7-2\right)}\)
\(=\frac{2.\left(-1\right)}{-1}=2\)
Vậy đáp án C đúng.