a) 19/37 + (1 - 19/37)

= (19/37  - 19/37) + 1

=  0 + 1 = 1

b) 15,27 - 4,13 - 1,14

= 15,27 - ( 4,13 + 1,14)

= 15,27 - 5,27

= 10

c) 60 - 13,75 - 26,25

= 60 - ( 13,75 + 26,25)

= 60 - 40

= 20

a) 19/37 + ( 1 - 19/37 )

= ( 19/37 - 19/37 ) + 1

= 0 + 1

= 1

b) 15,27 - 4,13 - 1,14

= 15,27 - ( 4,13 + 1,14 )

= 15,27 - 5,27

= 10

c) 60 - 13,75 - 26,25

= 60 - ( 13,75 + 26,25 )

= 60 - 40

= 20

a) \(\frac{19}{37}+\left(1-\frac{19}{39}\right)\)

\(=\left(\frac{19}{37}-\frac{19}{37}\right)+1\)

\(=1\)

b) 15.27 - 4.13 - 1.14

= 15.27 - ( 4.13 + 1.14 )

= 15.27 - 5.27

= 10

c) 60 - 13.75 - 26.25

= 60 - ( 13.75 + 26.25 )

= 60 - 40

= 20

Ở phần ... sẽ có tiếp là : 6 * 11 +        7 * 12 +                             8 * 13 +            9 * 14 +        10 * 15 +          11* 16          + 12 * 17 +                   13 * 18 +          14 * 19 +                    15 * 20 +           16 * 21 +              17 * 22 +     18 * 23 

= 24 + 36 + 50 + 66 + 84 + 104 + 126 + 150 + 176 + 204 + 234 + 266 + 300 + 336 + 374 + 414 

= 60 +  50 + 66 + 84 + 104 + 126 + 150 + 176 + 204 + 234 + 266 + 300 + 336 + 374 + 414 

= 110 + 66 + 84 + 104 + 126 + 150 + 176 + 204 + 234 + 266 + 300 + 336 + 374 + 414 

vì làm từng cái hơi lâu , lại khó nhìn nên mk đưa ra kết quả lun 

= 2944. 

k mk nha 

Phải là tính nhanh cơ

   1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20

= (1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+(10+20)

=   20   +   20   +   20   +   20  +   20    +   20  +   20   +    20   +   20  +30

=  20x9 +30

=180+30

=210

tk cho mik nhé

\(\frac{\left(20+1\right)x20}{2}\)

=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+10

=20+20+20+20+20+20+20+20+20+10

=190

a) =25-13+8=20

b) =7-12+43-(2+19-34)=38+13=51

15*17*19*21=101745

ta lay 101745*5=508725

15 * 17 * 19 * 21 * y = 508a25

5 * 3 * 17 * 19 * 7 * 3 * y = 508a25

5 * 9 * 17 * 19 * 7 * y = 508a25

==> 508a25 phải : hết cho 9

==> a = 1 ; 4 ; 7

15 * 17 * 19 * 21 * y = 508a25

5 * 3 * 17 * 19 * 7 * 3 * y = 508a25

5 * 9 * 17 * 19 * 7 * y = 508a25

==> 508a25 phải : hết cho 9

==> a = 1 ; 4 ; 7

\(A=\frac{17^{18}+1}{17^{19}+1}\)

\(17A=\frac{17^{19}+17}{17^{19}+1}=\frac{\left(17^{19}+1\right)+16}{17^{19}+1}=1+\frac{16}{17^{19}+1}\)

\(B=\frac{17^{17}+1}{17^{18}+1}\)

\(17B=\frac{17^{18}+17}{17^{18}+1}=\frac{\left(17^{18}+1\right)+16}{17^{18}+1}=1+\frac{16}{17^{18}+1}\)

\(\text{Vì}\)\(1+\frac{16}{17^{19}+1}< 1+\frac{16}{17^{18}+1}\)

\(\Leftrightarrow17A< 17B\)

\(\Leftrightarrow A< B\)

Trả lời

\(17A=\frac{\left(17^{18}+1\right)17}{17^{19}+1}=\frac{17^{19}+17}{17^{19}+1}=\frac{17^{19}+1+16}{17^{19}+1}=\frac{17^{19}+1}{17^{19}+1}+\frac{16}{17^{19}+1}=1+\frac{16}{17^{19}+1}\)

\(17B=\frac{\left(17^{17}+1\right)17}{17^{18}+1}=\frac{17^{18}+17}{17^{18}+1}=\frac{17^{18}+1+16}{17^{18}+1}=\frac{17^{18}+1}{17^{18}+1}+\frac{16}{17^{18}+1}=1+\frac{16}{17^{18}+1}\)

Vì \(17^{19}+1>17^{18}+1\)

\(\Rightarrow\frac{16}{17^{18}+1}>\frac{16}{17^{19}+1}\)

\(\Rightarrow1+\frac{16}{17^{18}+1}>1+\frac{16}{17^{19}+1}\)

\(\Rightarrow B>A\)

1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

= (1 + 19) + (3 + 17) + (5 + 15) + (7 + 13) + (9 + 11)

= 10 + 10 + 10 + 10 + 10

= 50

#Học tốt!!!

~NTTH~

1+3+5+7+9+11+13+15+17+19=(1+19)+(3+17)+(5+15)+(7+13)+(9+11)=20+20+20+20+20=100

1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

Ta có :

( 1 + 19 ) + ( 3 + 17 ) + ( 5 + 15 ) + ( 7 + 13 ) + ( 9 + 11 )

= 20 + 20 + 20 + 20 + 20

= 20 x 5

= 100

1) x - 23 + x = x - 18

   x + x - x     = -18 + 23

      x            = 5

2) x - 17 - 31 = -15 - 28

   x                 = -15 - 28 + 17 + 31

   x                 = 5

3) 28 - 37 - 18 = x - 32 + 19

    x                  = -32 + 19 - 28 + 37 + 18

    x                  = 14

Tích mình 3 mình tích lại 5 nhớ phải kết bạn nhé

\(a,1-\frac{9}{100}=\frac{91}{100}=\frac{910}{1000}\)

    \(1-\frac{99}{1000}=\frac{909}{1000}\)

Vì \(\frac{910}{1000}>\frac{909}{1000}\)nên\(\frac{9}{100}< \frac{99}{1000}\)

\(b,\frac{19}{21}< 1< \frac{27}{23}\)nên \(\frac{19}{21}< \frac{27}{23}\)

\(c,14< 28,99>100\)nên \(\frac{14}{99}< \frac{28}{100}\)

Câu c cách khác : \(\frac{28}{100}=\frac{14}{50}>\frac{14}{99}\)