a) -79 - 79.99 = -79(1 + 99) = -79.100 = -7900

b) -123.47 + 47.23 = -47(123 - 23) = -47.100 = -4700

c) 19 - 42.(-19) + 38.5 = 19 + 42.19 + 38.5 = 19(1 + 42 + 10) = 19.53 = 20.53 - 53 = 1060 - 53 = 1007

\(\frac{21.19+19.79}{38.50}\)

\(=\frac{19.\left(21+79\right)}{38.50}\)

\(=\frac{19.100}{38.50}\)

\(=\frac{19.2.50}{19.2.50}\)

\(=1\)

21 × 19 + 19 × 79 / 38 × 50

= 21 × 19 + 0,79

= ( 20 + 1 ) ×  19 + 0,79

= 20 × 19 + 1 × 19 + 0,79

= 380 + 19 + 0,79

= 399 + 0,79

= 399,79

\(\frac{21\cdot19+19\cdot79}{38\cdot50}\)

\(=\frac{19\left(21+79\right)}{38\cdot50}\)

\(=\frac{19\cdot100}{38\cdot50}\)

\(=\frac{19\cdot50\cdot2}{19\cdot2\cdot50}=1\)

₁₎ ( 2002 - 79 + 15 ) - ( -79 + 15 ) = 2002 

₂₎ - (515 - 80+ 91 ) - ( 2003 + 80 + 91 ) = -2700 

₃₎ 4573 + 46 - 4573 + 35 - 16 - 5 = 60

₄₎ 32 + 34 + 36 + 38 - 10 - 12 - 14 - 16 - 18 = 70 

cái này mà lớp 2 hả bạn

79-16+11+10+26.      

=(79+11)+(-16+26)+10.      

=90+10+10.  

= 110.          

20-19+39-38+26-25+10.        

=(20-19)+(39-38)+(26-25)+10.      

=1+1+1+10.        

=13.     

110 VÀ 13

a,79.101=79.(100+1)

= 79.100 + 79

=7900 + 79 = 7979

b,(1999+2016)-1999 = 1999 - 1999 + 2016 = 0 + 2016 = 2016

c,81+250+19 =(81 + 19) + 250 = 100 + 250 = 350

d,165+79+135 =(165+135)+79=300+79=379

e,35.45+35.55=35.(45+55)

= 35.100

=3500

f,5.125.2.8=(5.2).(125.8)

= 10 . 1000

= 10 000

a) 79. 101

= 79 . (100 + 1)

= 79. 100 + 79

= 7 900 + 79

= 7 979

b) (1 999 + 2 016) - 1 999

= ( 1 999 - 1 999) + 2 016

= 0 + 2 016

= 2 016

c) 81 + 250 + 19

= (81 + 19) + 250

= 100 + 250

= 350

d) 165 + 79 + 135

= (165 + 135) + 79

= 300 + 79

= 379

e) 35 . 45 + 35 . 55

= 35 . (45 + 55)

= 35. 100

= 3 500

f) 5. 125 . 2. 8

= (5 . 2) . (125 . 8)

= 10 . 1 000

= 10 000

1) 125.(-24) + 24.225.

\(=24\left(-125+225\right)=24.100=2400.\)

2) 512.(2 – 128) – 128. (-512).

\(=512\left(2-128+128\right)=512.2=1024.\)

a) 34+35+...+78+79

So so hang cua day tren la:

           (79-34):1+1=46( so )

Tong cua day tren la:

           (79+34)x46:2=2599

                 DS:2599

Câu a bạn @Conan làm rồi

mik làm câu b

\(\text{= 24.25 + 24.37 + 24.38 = 24.(25+37+38) = 24.100 = 2400}\)

\(\frac{67}{43}+\frac{106}{79}+\frac{52}{79}+\frac{19}{43}\)

\(=\left(\frac{67}{43}+\frac{19}{43}\right)+\left(\frac{106}{79}+\frac{52}{79}\right)\)

\(=2+2\)

\(=4\)

\(Ta\) \(có\)

\(\frac{67}{43}+\frac{106}{79}+\frac{52}{79}+\frac{19}{43}\)

\(=\left(\frac{67}{43}+\frac{19}{43}\right)+\left(\frac{106}{79}+\frac{52}{79}\right)\)

\(=\frac{86}{43}+\frac{158}{79}\)

\(=\frac{6794}{3397}+\frac{6794}{3397}\)

\(=\frac{13588}{10094}=\frac{6794}{5047}\)

bang 2 nha em de nhu the nay ma