2+2+2+2+2+2+2+2+2+2+2+..........+2 (235 số 2)=2.235=470

4+4+4+4+4+4+4+4+4+4+44+4=4.11+44=44.2=88

6+66+666+6666+66666=6+6.11+6.111+6.1111+6.11111=6.(1+11+111+1111+11111)=6.12345=74070

=2*235=470

4*12=48

6*1239=74394

2+2+2+2+2+2+2+2+2+2+2+..........+2 (235 số 2)=470

4+4+4+4+4+4+4+4+4+4+44+4=88

6+66+666+6666+66666=74070

số các số hạng :

 ( 50 - 1 ) : 1 +1 = 50 ( số )

tổng  :

  ( 50 + 1 ) x 50 : 2 = 1275

đs:...

bài 2 :

số các số hạng :

  ( 44 - 2 ) : 2 + 1 = 22 ( số )

tổng :

   ( 44 + 2 ) x 22 : 2 = 506

đs:...

\(=5+\dfrac{2}{5}+4+\dfrac{3}{7}-\dfrac{1}{4}+\dfrac{4}{7}-2-\dfrac{2}{5}-\dfrac{3}{4}\)

\(=\left(5+4-2\right)+\left(\dfrac{2}{5}-\dfrac{2}{5}\right)+\left(\dfrac{3}{7}+\dfrac{4}{7}\right)-\dfrac{1}{4}-\dfrac{3}{4}\)

=7+1-1

=7

`#lv`

`5 2/5 + 4 3/7 - 1/4 + 44/77 - 2 2/5 - 0,75`

`= 27/5 + 31/7 - 4/7 - 12/5 - 3/4`

`= (27/5 - 12/5) + (31/7 - 4/7) + ( 1/4 + 3/4)`

`= 3 + 27/7 + 1`

`= 4 + 27/7`

`= 28/7 + 27/7`

`= 56/7`

`= 8`

tíc cho mình nha

2/3 - 7/24 = 3/8 

\(\frac{2}{3}-\left(\frac{1}{6}+\frac{1}{8}\right)\)=\(\frac{16}{24}-\left(\frac{4}{24}+\frac{3}{24}\right)\)=\(\frac{16}{24}-\frac{7}{24}=\frac{9}{24}=\frac{3}{8}\)

1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9+0+0+0+3+4+1+2+3+111+44+99 = 357

1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9+0+0+0+3+4+1+2+3+111+44+99=357