\(A=\frac{3}{8^3}+\frac{7}{8^4}=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^4}\)

\(B=\frac{7}{8^3}+\frac{3}{8^4}=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^4}\)

\(A=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^3}>B=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^4}\)

vậy A>B

A=(24+7)/8^4 =31/8^4 
B=(56+3)/8^4 = 59/8^4 
=> A<B

a:Đ b:S  c:Đ  d:Đ

alo\

A .Đ

B.S

C.Đ

D.Đ

\(a.\frac{1}{7}\times\frac{-3}{8}+\frac{-13}{8}==\frac{-3}{56}+\frac{-13}{8}=\frac{-3}{56}+\frac{-91}{56}=\frac{-94}{56}=\frac{-47}{28}\)

\(b.\frac{3}{5}\times\frac{13}{40}-\frac{1}{10}\times\frac{16}{23}=\frac{39}{200}-\frac{8}{115}=\frac{577}{4600}\)

\(c.\left(\frac{-3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left(\frac{3}{5}+\frac{1}{4}\right):\frac{3}{7}\)

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

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

\(=\frac{7}{3}\times\left[\left(\frac{-3}{4}+\frac{1}{4}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)\right]\)

\(=\frac{7}{3}\times\left(\frac{-2}{4}+1\right)\)

\(=\frac{7}{3}\times\frac{1}{2}\)

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

\(d.\frac{7}{8}:\left(\frac{2}{9}-\frac{1}{8}\right)+\frac{7}{8}:\left(\frac{1}{6}-\frac{5}{12}\right)\)

\(=\frac{7}{8}:\frac{7}{72}+\frac{7}{8}:\left(\frac{-1}{4}\right)\)

\(=\frac{7}{8}\times\frac{72}{7}+\frac{7}{8}\times-4\)

\(=\frac{7}{8}\times\left(\frac{72}{7}+\left(-4\right)\right)\)

\(=\frac{7}{8}\times\frac{44}{7}\)

\(=\frac{11}{2}\)

= 1*2*3*4*5*6*7*8*(9-1-8)

=1*2*3*4*5*6*7*8*0

=0

tơ dùm

\(A=1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9-1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8-1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot8\)

\(=1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9-1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot1-1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot8\)

\(=1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot\left(9-1-8\right)\)

\(=1\cdot2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot0=0\)

A

254;948

1a

 2  254;948

a

254,948

Phương pháp giải:

- Đếm số lượng các số hạng giống nhau của mỗi tổng.

- Viết phép nhân thích hợp.

Lời giải chi tiết:

a) 2 + 2 + 2 + 2 + 2 = 2 × 5

b) 5 + 5 + 5 + 5 = 5 × 4

c) 8 + 8 + 8 = 8 × 3

d) 4 + 4 + 4 = 4 × 3

e) 7 + 7 + 7 + 7 + 7 = 7 × 5

g) 10 + 10 = 10 × 2

a.90

b.6

a, 90

b,6

a:=90

b:=6