4: \(=\dfrac{2+3}{7}+\dfrac{1+6}{9}-\dfrac{5}{6}=\dfrac{5}{7}+\dfrac{7}{9}-\dfrac{5}{6}=\dfrac{83}{126}\)

5: \(=\dfrac{-5-2}{7}+\dfrac{3+1}{4}-\dfrac{1}{5}=-\dfrac{1}{5}\)

6: \(=\dfrac{-3-28}{31}+\dfrac{-6-1}{17}+\dfrac{1-5}{25}=-1-\dfrac{7}{17}-\dfrac{4}{25}=-\dfrac{668}{425}\)

4. \(\dfrac{2}{7}+\dfrac{1}{9}+\dfrac{3}{7}+\dfrac{5}{9}+\dfrac{-5}{6}\)

\(=\left(\dfrac{2}{7}+\dfrac{3}{7}\right)+\left(\dfrac{1}{9}+\dfrac{5}{9}\right)+\dfrac{-5}{6}\)

\(=\dfrac{5}{7}+\dfrac{2}{3}+\dfrac{-5}{6}\)

\(=\dfrac{30+28+\left(-35\right)}{42}=\dfrac{23}{42}\)
 

5. \(\dfrac{-5}{7}+\dfrac{3}{4}+\dfrac{-1}{5}+\dfrac{-2}{7}+\dfrac{1}{4}\)

\(=\left(\dfrac{-5}{7}+\dfrac{-2}{7}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\dfrac{-1}{5}\)

\(=\dfrac{-7}{7}+\dfrac{4}{4}+\dfrac{-1}{5}\)

\(=-1+1+\dfrac{-1}{5}\)

\(=-\dfrac{1}{5}\)
 

6. \(\dfrac{-3}{31}+\dfrac{-6}{17}+\dfrac{1}{25}+\dfrac{-28}{31}+\dfrac{-1}{17}+\dfrac{-1}{5}\)

\(=\left(\dfrac{-3}{31}+\dfrac{-28}{31}\right)+\left(\dfrac{-6}{17}+\dfrac{-1}{17}\right)+\dfrac{1}{25}+\dfrac{-1}{5}\)

\(=\dfrac{-31}{31}+\dfrac{-7}{17}+\dfrac{1}{25}+\dfrac{-1}{5}\)

\(=-1+\dfrac{-7}{17}+\dfrac{1}{25}+\dfrac{-1}{5}\)

\(=\dfrac{-425+\left(-175\right)+17+\left(-85\right)}{425}=\dfrac{-668}{425}\)

a) 2012 - ( 304 + 2012 ) + ( 2013 + 304 )

= 2012 - 304 - 2012 + 2013 + 304 

= 2012 + ( - 304 ) + ( - 2012 ) + 2013 + 304

= [ 2012 + ( - 2012 ) ] + [ ( - 304 ) + 304 ] + 2013

= 0 + 0 + 2013

= 2013

b) \(\frac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}\)

\(=\frac{\left(3^2\right)^{14}.\left(5^2\right)^5.\left(2^3\right)^7}{\left(3^2.2\right)^{12}.\left(5^4\right)^3.\left(2^3.3\right)^3}\)

\(=\frac{3^{28}.5^{10}.2^{21}}{3^{24}.2^{12}.5^{12}.2^9.3^3}\)

\(=\frac{3^{28}.5^{10}.2^{21}}{3^{27}.5^{12}.2^{21}}\)

\(=\frac{3}{5^2}=\frac{3}{25}\)

a) 2012 - ( 304 + 2012 ) + (2013 + 304 )

= 2012 - 304 +2012 + 2013 + 304

= ( 2012 - 2012 ) + ( 304 + 304 ) + 2013

= 0 + 608 + 2013

= 2621

Chờ một chút để minh suy nghĩ 

ok bạn

5⁴-2.5³

=5.5³-2.5³

=5³.(5-2)

=5³.3

=125.3

=375

k nhé!

Thank you ! + 1 k

5⁴-2.5³

=5.5³-2.5³

=5³.(5-2)       (tính chất phân phối)

=5³.3

=125.3=375

1) 5 + (-4) = 1

2) (-8) + 2 = -6

3) 8 + (-2) = 6

4) 11 + (-3) = 8

5) (-11) + 2 = -9

6) (-7) + 3 = -4

7) (-5) + 5 = 0

8) 11 + (-12) = -1

9) (-18) + 20 = 2

10) (15) + (-12) = 3

11) (-17) + 17 = 0

12) 16 + (-2) = 14

13) (30) + (-14) = 16

14) (-19) + 20 = 1

15) (-18) + 15 = -3

16) (10) + (-6) = 4

17) (-28) + 14 = -14

18) 15 + (-30) = -15

19) (15) + (-4) = 11

20) (-21) + 11 = -10

21) 8 + (-22) = -14

22) (-15) + 4 = -11

23) (-3) + 2 = -1

24) 17 + (-14) = 3

25) 17 + (-14) = 3

thế này đọc đc mới đỉnh

theo máy tính kết quả là: \(\frac{13775}{11}\)

tự làm đi dễ mà

10\(^3\) + 2. 5\(^3\) + \(\frac{5^3}{55}\)

= 1000 + 2. 125 + \(\frac{125}{55}\)

= 1000 + 250 + \(\frac{25}{11}\)

= 1250 + \(\frac{25}{11}\)

= 1250\(\frac{25}{11}\) =\(\frac{\text{ 89575}}{88}\)