a) (39 - 2689) + 2689

= 39 + (2689 - 2689)

= 39 + 0

= 39

__

b) - (12 345 - 999) = - (12 345 - 1000+1)

- 12 345 + 12345 + 999 -1000+ 1 = 0

0=0

----

c) (-1312) - (1998 - 1312) 

= (1312 - 1312) - 1998

= 0 - 1998 = -1998

d) (-6955) - 33 - 45 -  (-133)

= -(6955+45) - (33 - 133) 

= -7000 - (-100)

= -7000 + 100 = -6900

e) (-21) - 23 - [16 - (-18) - 18 - 16] + 2144

= -21 - 23 - 16 - 18 + 18 + 16 + 2144

= (16 - 16) + (18 - 18) + (2144 - 21 - 23)

= 0 + 0 + 2100

= 2100

g) (-2020) - 2018 - 2016 - ...-2008

= - [(2020+ 2008): 2 x 7]

= -[(4028): 2 x 7]

= -[2014 x 7]

= - 14098

33.(17 – 5) – 17.(33 -5)

= 33. 17 – 33.5 – 17.33 + 17.5

= (33.17 – 33. 17) + ( 17.5 – 33.5)

= 0 + 5.(17- 33)

= 5.(- 16) = -80

mk làm câu b phần 1 thui tại vì câu a phần 1 và 2 DLT làm đúng rồi

b)33.(17-5)-17.(33-5)

=33.17-33.5-17.33-17.5

=(33.17-17.33)-(33.5-17.5)

=0.(33.5-17.5)

=0

a)\(25\cdot\left(-7\right)\cdot4=25\cdot4\cdot\left(-7\right)\)

=\(\left(-7\right)\cdot100=-700\)

b)\(33\cdot\left(17-5\right)-17\cdot\left(33-5\right)\)

=\(33\cdot12-17\cdot28\)

=\(-80\)

2) \(\frac{3}{4}\)giờ =\(45\)phút

a) \(25.\left(-7\right).4=\left(25.4\right).\left(-7\right)=100.\left(-7\right)=-700\)

b) \(33.\left(17-5\right)-17.\left(33-5\right)=33.17-33.5-17.33+17.5=5.\left(17-33\right)\)\(=5.\left(-16\right)=-80\)

25.(-7).4

=(25.4).(-7)

=100.(-7)

=-700

a.18.17-3.6.7
 =18.17-18.7
 =18.(17-7)
 =18.10=180
b.54-6.(17+9)
 =54-6.26
 =54-156=-102
c.33.(17-5)-17.(33-5)
 =33.17-33.5-17.33+17.5
 =33.5+17.5
 =(33+17).5
 =50.5=250

`6/21-(-12/44)+10/14-(1/(-4))-18/33`

`=2/7+12/44+5/7-((-1)/4)-6/11`

`=2/7+3/11+5/7+1/4-6/11`

`=(3/11-6/11)+(2/7+5/7)+1/4`

`=-3/11+7/7+1/4`

`=43/44`

(-12)+(-13)+33+(-11)=-25+22=-3

Giair từng bước nha bạn .

A =\(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)

A = \(\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}\right)\)+ \(\frac{12}{19}\)

A = \(\frac{7}{19}.1+\frac{12}{19}\)

A = \(\frac{7}{19}+\frac{12}{19}\)

A = 1

--------

B = \(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)

B = \(\frac{5}{9}.\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)\)

B = \(\frac{5}{9}.1\)

B = \(\frac{5}{9}\)

-------

C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).\left(\frac{1}{3}-\frac{1}{4}-\frac{1}{12}\right)\)

C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).\left(\frac{4}{12}-\frac{3}{12}-\frac{1}{12}\right)\)

C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).0\)

C = 0

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