\(1\dfrac{14}{15}-\dfrac{5}{17}-\dfrac{12}{17}-\dfrac{14}{15}\\ =\left(1\dfrac{14}{15}-\dfrac{14}{15}\right)-\left(\dfrac{5}{17}+\dfrac{12}{17}\right)\\ =\left[1+\left(\dfrac{14}{15}-\dfrac{14}{15}\right)\right]-1=1-1=0\)

a) 5.2² - 18 : 3

= 5.4 - 18 : 9

= 20 - 2

= 18

b) 17 . 85 + 15 . 17 - 120

= 17 . (85 + 15) - 120

= 17 . 100 - 120

= 1700 - 120

= 1580

c) 2³ . 17 - 2³ . 14

= 8 . 17 - 8 . 14

= 8 . (17 - 14)

= 8 . 3

= 24

a) 5 . 2² – 18 : 3² 

= 5.4 – 18 : 9

= 20 – 2

= 18

b) 17 . 85 + 15 . 17 – 120

= 17. (85 + 15) – 120

= 17.100 – 120

= 170 – 120

= 50

c) 2³ . 17 – 2³ . 14

= 2³.(17 - 14)

= 2³.3

= 8.3

= 24

a) 18

b) 50

c) 24

a=240

b=45

c=-1700

a, - ( - 9 ) . 5 . ( -3 ) . 2 

 =  [ - ( - 9 ) . ( - 3 ) ] . ( 5 . 2 ) 

= - 27 . 10 

= - 270 

c,  37. ( - 17 ) + ( - 17 ) . 63 

= ( - 17 ) . ( 63 + 37 ) 

= ( - 17 ) . 100 =   - 1700 

b,  ý này mk ko hiểu đề bài lắm :( 

Câu 9

a) 2/15 + (-3/5)

= 2/15 - 3/5

= 2/15 - 9/15

= -7/15

b) -5/7 + 3/7 . (-2/9)

= -5/7 - 2/21

= -15/21 - 2/21

= -17/21

c) 5/16 - (7/15 - 3/16) + 17/30

= 5/16 - 7/15 + 3/16 + 17/30

= (5/16 + 3/16) + (17/30 - 14/30)

= 1/2 + 1/10

= 5/10 + 1/10

= 6/10

= 3/5

\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)

\(a,\dfrac{3}{5}+\dfrac{1}{5}.\dfrac{-17}{9}=\dfrac{3}{5}-\dfrac{17}{45}=\dfrac{27}{45}-\dfrac{17}{45}=\dfrac{10}{45}=\dfrac{2}{9}\\ b,\left(-\dfrac{4}{15}-\dfrac{18}{19}\right)-\left(\dfrac{20}{19}+\dfrac{11}{15}\right)=-\dfrac{4}{15}-\dfrac{18}{19}-\dfrac{20}{19}-\dfrac{11}{15}=\left(-\dfrac{4}{15}-\dfrac{11}{15}\right)-\left(\dfrac{18}{19}+\dfrac{20}{19}\right)=-1-2=-3\)

\(a,=\dfrac{3}{5}+\left(-\dfrac{17}{45}\right)=\dfrac{2}{9}\)

\(b,=-\dfrac{4}{15}-\dfrac{18}{19}-\dfrac{20}{19}-\dfrac{11}{15}=-3\)

a. 3/5+1/5.-17/9

=3/5+-17/45

=27/45+-17/45

=2/9

b. (-4/15-18/19)-(20/19+11/15)

=-4/15-18/19-20/19-11/15

=(-4/15-11/15)-(18/19-20/19)

=(-1)-(-2/19)

=(-19/19)-(-2/19)

=-17/19  

a.2/9
b.-3

a.2/9 b.(-3)

a.2/9
b.-3

a)5*2^2-18:3=20-6=14

b)17*85+15*17-120=17*(120-85+15)=17*20=340

c2^3*17-2^3*14=2^3(17-14)=8*3=24