\(\dfrac{1}{2}-\dfrac{1}{2}:x=\dfrac{3}{4}\\ =>\dfrac{1}{2}:x=\dfrac{1}{2}-\dfrac{3}{4}=-\dfrac{1}{4}\\ =>x=\dfrac{1}{2}:\left(-\dfrac{1}{4}\right)=-2\)

`1/2 - 1/2 : x =3/4`

`1/2 : x = 1/2 -3/4`

`1/2:x=2/4-3/4`

`1/2:x=-1/4`

`x=1/2:(-1/4)`

`x=1/2.(-4)`

`x=-2`

`(x+1)+(x+2)+.....+(x+211)=23632`

`x+1+x+2+......+x+211=23632`

`(x+x+.....+x)+(1+2+.....+211)=23632`

Khoảng cách : `1`

Số hạng :

`(211-1)/1 + 1 =211(số-hạng)`

Tổng:

`(211+1).211:2=22366`

`=> 211x + 22366 = 23632`

`211x = 23632 - 22366`

`211x = 1266`

`x=1266:211`

`x=6`

Vậy `x=6`

\(\left(x+1\right)+\left(x+2\right)+...+\left(x+211\right)=23632\\ \left(x+x+...+x\right)+\left(1+2+...+211\right)=23632\\ x\times211+\left(211+1\right).211:2=23632\\ x\times211+22366=23632\\ x\times211=1266\\ x=6\)

Viết thêm số mấy vậy bạn?

\(\overline{abba}=\overline{a00a}+\overline{bb0}\\ =a\times1000+a+b\times100+b\times10\\ =a\times1001+b\times110\\ =11\times\left(a\times91+b\times10\right)⋮11\)

`0,5 + 1/3 + 0,4 + 5/7 + 1/6 - 4/35`

`=1/2 + 1/3 + 2/5 + 5/7 + 1/6 - 4/35`

`=(1/2 + 1/3 + 1/6) +(2/5+5/7-4/35)`

`=(3/6+2/6+1/6)+(14/35 +25/35-4/35)`

`=6/6 + 35/35`

`=1+1`

`=2`

`4/20 + 16/42 + 6/15 + (-3/5) + 2/21 + (-10)/21 + 3/20`

`=4/20 + 16/42 + 6/15 -3/5 +2/21 - 10/21 + 3/20`

`=1/5 + 8/21 + 2/5 - 3/5 +2/21 - 10/21 + 3/20`

`=(1/5 + 2/5 - 3/5) + (8/21 + 2/21 - 10/21) + 3/20`

`=` \(\left(\dfrac{1+2-3}{5}\right)+\left(\dfrac{8+2-10}{21}\right)+\dfrac{3}{20}\)

`=0+0+3/20`

`=3/20`