11/23 × 12/17+11/23×5/17+12/23

=(11/23+12/23) x  (12/17+5/17) 

=1 x 1

=1

11/23 × 12/17+11/23×5/17+12/23

=11/23 × 12/17+11/23×5/17+12/23x1

=11/23 × (12/17+5/17+1)

=11/23 ×       2

=  22/23

a) dấu >

b)  dấu >

a) 23¹⁷ - 23¹⁶ = 23¹⁶(23-1) = 23¹⁶.22

23¹⁶ - 23¹⁵  = 23¹⁵( 23-1) = 23¹⁵.22

Do........... ( tới đây chắc bn làm đc)

b) 17¹⁹ + 17¹⁷ = 17¹⁷( 17²+ 1) = 17¹⁷. ( 289+1) = 17¹⁷ . 290 

2 .17¹⁸  = 17¹⁷ . (17.2) = 17¹⁷. 34

Do..................

a)5.4 – 18 : 9              b)17. (85 + 15) – 120

= 20 – 2                     = 17.100 – 120 

= 18                            = 170 – 120 

                                   = 50

c)2³.(17 - 14)

= 2³.3

= 8.3

= 24

a) 5 . 2\(^2\) - 18 : 3

⇔ 5 . 4 - 18 : 3

⇔ 20 - 6

⇔ 14

b) 17 . 85 + 15 . 17 - 120

⇔ 17 . ( 85 + 15 ) - 120

⇔ 17 . 100 - 120

⇔ 1700 - 120

⇔ 1580

c) 2\(^3\) . 17 - \(2^3\) . 14

⇔ \(2^3\) . ( 17 - 14 )

\(\Leftrightarrow\) 8 . 3

⇔ 24

=(13-13).(23-17)

=0.6

=0

ảo

\(=\dfrac{17}{23}\cdot\dfrac{23}{17}\cdot\dfrac{1}{2}\cdot\dfrac{3}{4}\cdot\left(-80\right)=-80\cdot\dfrac{3}{8}=-30\)

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

\(=\dfrac{9}{23}\left(\dfrac{5}{17}-\dfrac{22}{17}\right)+11+\dfrac{9}{23}=11\)

\(=\dfrac{8}{23}+\dfrac{3}{19}-\dfrac{15}{17}-\dfrac{2}{17}+\dfrac{15}{23}=\dfrac{3}{19}\)

\(\left(\dfrac{8}{23}+\dfrac{3}{19}-\dfrac{15}{17}\right)-\left(\dfrac{2}{17}-\dfrac{15}{23}\right)\\ =\dfrac{8}{23}+\dfrac{3}{19}-\dfrac{15}{17}-\dfrac{2}{17}+\dfrac{15}{23}\\ =\left(\dfrac{8}{23}+\dfrac{15}{23}\right)-\left(\dfrac{15}{17}+\dfrac{2}{17}\right)+\dfrac{3}{19}\\ =1-1+\dfrac{3}{19}\\ =\dfrac{3}{19}\)

Lời giải:
a.

$21\times 23-3\times 7\times (-17)$

$=21\times 23-21\times (-17)$

$=21\times 23+21\times 17=21\times (23+17)=21\times 40$

$=840$

b.

$42\times 3-7\times [(-34)+18]$

$=7\times 18-7\times (-16)$

$=7\times 18+7\times 16=7\times (18+16)=7\times 34=238$

c.

$=142\times 32+32\times (-7)-13\times 32$

$=32\times (142-7-32)=32\times 103=3296$

d.

$=13\times [(23-17)-(23+17)]$

$=13\times (23-17-23-17)=13\times (-34)=-442$