5/6 x 1/7 - 1/7 x 1/6

= 1/7 x (5/6 - 1/6)

= 1/7 x 2/3

= 2/21

8/15 : 4/5 x 3/2

= 2/3 x 3/2

= 1

a: =1/7(5/6-1/6)=1/7x2/3=2/21

b: =8/15x5/4x3/2=1

`5/6xx1/7-1/7xx1/6`

`= 1/7 xx (5/6-1/6)`

`= 1/7 xx 2/3`

`= 2/21`

`8/15: 4/5 xx3/2`

`= 2/3 xx 3/2`

`= 1`

Bài 1 :

Gọi \(A=5+5^2+5^3+...+5^{98}+5^{99}\\ 5A=5^2+5^3+5^4+...+5^{99}+5^{100}\\ 5A-A=\left(5^2+5^3+5^4+...+5^{99}+5^{100}\right)-\left(5+5^2+5^3+...+5^{98}+5^{99}\right)\\ 4A=5^{100}-5\\ A=\dfrac{5^{100}-5}{4}\)

Bài 2:

\(\left(12x-4\right)\cdot8^{2022}=4\cdot8^{2023}\\ 12x-4=4\cdot8^{2023}:8^{2022}\\ 12x-4=4\cdot8\\ 12x-4=32\\ 12x=36\\ x=3\)

 5 + (-12)-10 = (-7) - 10 = -17

   \(5 + (-12) - 10\)

\(= 5 - 12 - 10\)

\(= (-7) - 10\)

\(= -17\)

-2 nhé em yêu

16.9454545455

\(=\left(1,1+1,9\right)+\left(1,2+1,8\right)+\left(1,3+1,7\right)+\left(1,4+1,6\right)+1,5\)
\(=3+3+3+3+1,5\)
\(=13,5\)

1,1 + 1,2 + 1,3 + 1,4 + 1,5 + 1,6 + 1,7 + 1,8 + 1,9

= ( 1,1 + 1,9 ) + ( 1,2 + 1,8 ) + ( 1,3 + 1,7 ) + ( 1,4 + 1,6 ) + 1,5

=     3 + 3 + 3 + 3 + 1,5

= 3 \(\times\) 4 + 1,5 

= 12 + 1,5

= 13,5

\(\left(\dfrac{2}{3}-\dfrac{1}{4}+\dfrac{5}{11}\right)-\left(5-\dfrac{1}{3}-\dfrac{6}{5}\right)-\left(6-\dfrac{7}{4}+\dfrac{3}{2}\right)\)

\(=\left(\dfrac{88-33+60}{132}\right)-\left(\dfrac{75-5-18}{15}\right)-\left(\dfrac{24-7+6}{4}\right)\)

\(=\dfrac{115}{132}-\dfrac{52}{15}-\dfrac{23}{4}\)

\(=-8\dfrac{19}{55}\)

=1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 +1/7 

=1/3 - 1/6 + 1/7

= 1/6 +1/7

=13/42

=\(\frac{1}{3}\) - \(\frac{1}{4}\) + \(\frac{1}{4}\) - \(\frac{1}{5}\) + \(\frac{1}{5}\) - \(\frac{1}{6}\) +\(\frac{1}{7}\)

=\(\frac{1}{3}-\frac{1}{6}+\frac{1}{7}\)

= \(\frac{1}{6}+\frac{1}{7}\)

=\(\frac{13}{42}\)

hoang tu may trang giai thich gium to voi

cho to hoi co phai cau hoc lop 7 khong

=1+(2-3-4+5)+3-4-5+6)+...+(200-201-202+203)+204

=1+0+0+...+0+204

=1+204

=205

tinh 

1+2 -3 -4 +5+3-4-5+6 +4-5-6 +7 + ....+200-201 -202 + 203 + 204 =1+0+...+0+204=1+204=205.

bn k cho mik nha. ^-^ thanks bn trc.

ban oi minh chua hoc so am 

giống bài mình cần mà ko có ai trả lời nhỉ

mong mọi người vô giúp 2 đứa mình với

B=81.(12.(1-1/7-1/289-1/85)/4.(1-1/7-1/289-1/85:5.(1+1/13+1/169+1/91)/6.(1+1/13+1/169+1/91).158158158/711711711

  =81.(12/4:5/6).158.1001001/711.1001001

=81.18/5.158/711

=324/5