\(B=\left(1-\frac{1}{7}\right)\left(1-\frac{2}{7}\right)\left(1-\frac{3}{7}\right)...\left(1-\frac{2011}{7}\right)\)

\(B=\frac{6}{7}.\frac{5}{7}.\frac{4}{7}....\frac{-2004}{7}\)

Còn lại bạn tự tính đi.

Ta có: \(\left(3\dfrac{3}{4}+\dfrac{4}{7}\cdot\dfrac{7}{16}\right):\dfrac{1}{2}\)

\(=\left(\dfrac{15}{4}+\dfrac{1}{4}\right)\cdot2\)

\(=4\cdot2=8\)

 [ 3 và 3/4 + 4/7 x 7/16 ] : 1/2

mk gửi thiếu 3 và 3/4

\(\dfrac{1}{2}\times\dfrac{1}{3}+\dfrac{3}{4}\)

\(=\dfrac{1}{6}+\dfrac{3}{4}\)

\(=\dfrac{2}{12}+\dfrac{9}{12}\)

\(=\dfrac{11}{12}\)

____________________________

\(\dfrac{3}{7}-\dfrac{2}{7}:\dfrac{2}{3}\)

\(=\dfrac{3}{7}-\dfrac{2}{7}\times\dfrac{3}{2}\)

\(=\dfrac{3}{7}-\dfrac{3}{7}\)

\(=0\)

Chúc bạn học tốt

1/2 x 1/3 + 3/4 = 1/6 + 3/4 = 4/24 + 18/24 = 22/24 = 11/12
3/7 - 2/7 : 2/3 = 3/7 - 2/7 x 3/2 = 3/7 - 3/7 = 0

1​×31​+43​

=16+34=61​+43​

=212+912=122​+129​

=1112=1211​

____________________________

37−27:2373​−72​:32​

=37−27×32=73​−72​×23​

=37−37=73​−73​

$=0$

101/28

43/90

3/4:1/5-1/7

=15/4-1/7

=101/28

7/9-3/5.1/2

=7/9-3/10

=43/90

3/4 : 1/5 - 1/7

=> 3/4 x 5/1 - 1/7

=> 15/4 - 1/7

=> 105/28 - 4/28

=> 101/28

7/9 - 3/5 x 1/2

=> 7/9 - 3/10

=> 70/90 - 27/90

=> 43/90

kết quả bằng 1 đó bạn

Lời giải:

a.

$\frac{5}{15}-\frac{1}{6}\times \frac{2}{5}=\frac{5}{15}-\frac{1}{15}=\frac{4}{15}$

b.

$\frac{8}{24}+\frac{3}{4}:\frac{1}{8}=\frac{1}{3}+6=\frac{19}{3}$

c.

$\frac{1}{7}: \frac{2}{8}-\frac{1}{7}=\frac{1}{7}\times 4-\frac{1}{7}$

$=\frac{1}{7}\times (4-1)=\frac{1}{7}\times 3=\frac{3}{7}$

a: \(A=0x^2y^4z+\dfrac{7}{2}x^2y^4z-\dfrac{2}{5}x^2y^4z=\dfrac{31}{10}x^2y^4z=\dfrac{31}{10}\cdot2^2\cdot\dfrac{1}{16}\cdot\left(-1\right)=-\dfrac{31}{40}\)

a: \(=\dfrac{7}{5}x^4z^3y=\dfrac{7}{5}\cdot2^4\cdot\left(-1\right)^3\cdot\dfrac{1}{2}=-\dfrac{56}{5}\)

b: \(=-xy^3\)

\(=\dfrac{1}{2}\cdot\dfrac{6}{5}\cdot\dfrac{8}{7}+\dfrac{3}{7}\cdot\dfrac{9}{5}=\dfrac{24}{35}+\dfrac{27}{35}=\dfrac{51}{35}\)

\(=1^2-5\cdot1+7=8-5=3\)

They `x = 1` vào biểu thức. Ta có:

   `1^2 - 5 . 1 + 7 = 1 - 5 + 7 = 3`

thay x=1 vào biểu thức ta có 

1^2-5.1+7 = 1-5+7=-4+7=3

vậy giá trị biểu thức tại x=1 là 3