Hỏi đáp về Nhân, chia số hữu tỉ - Đại số 7

1.thực hiện phép tính

a.\(\dfrac{-5}{21}-\dfrac{1}{3}+3\dfrac{1}{2}.\left(\dfrac{-2}{3}\right)^3\)

b)\(-2\dfrac{1}{3}+\left(\dfrac{3}{8}-\dfrac{3}{4^{^{ }}}\right)^3:\dfrac{5}{9}-\dfrac{1}{2}\)

c)\(\left(6-2\dfrac{4}{5}\right).3\dfrac{1}{8}-1\dfrac{3}{5}:\left(-\dfrac{1}{2}\right)^2\)

d)\(-\dfrac{3}{7}.\dfrac{5}{9}+\dfrac{4}{7}.\dfrac{-1}{3}-\left(0,5\right)^3\)

e)\(\dfrac{15}{5}-\dfrac{2}{17}+\dfrac{15}{23}-\dfrac{15}{17}+\dfrac{4}{19}\)

Giúp mik nha mai mik phải nộp bài cho thầy rùi nì

BT1: Tìm x, biết:

6) \(\dfrac{x+1}{2017}+\dfrac{x+2}{2016}=\dfrac{x+3}{2015}-1\)

Cho số a = \(\left(\dfrac{9}{11}-0,81\right)^{2007}\)

Chứng minh rằng nếu viết dưới dạng số thập phân thì a sẽ có ít nhất 4000 chữ số 0 đầu tiên sau dấu phẩy.

A=(-2).\(\left(-1\dfrac{1}{2}\right)....\left(-1\dfrac{1}{1001}\right)\)

ĐỀ 1:

1. Tính:

a. \(\dfrac{7}{23}\left[\left(\dfrac{-8}{6}\right)-\dfrac{45}{18}\right]\)

b. \(\dfrac{1}{5}:\dfrac{1}{10}-\dfrac{1}{3}\left(\dfrac{6}{5}-\dfrac{9}{4}\right)\)

c. \(\dfrac{3}{5}.\left(\dfrac{-8}{3}\right)-\dfrac{3}{5}:\left(-6\right)\)

d. \(\dfrac{1}{2}\left(\dfrac{4}{3}+\dfrac{2}{5}\right)-\dfrac{3}{4}\left(\dfrac{8}{9}+\dfrac{16}{3}\right)\)

e. \(\dfrac{6}{7}:\left(\dfrac{3}{26}-\dfrac{3}{13}\right)+\dfrac{6}{7}\left(\dfrac{1}{10}-\dfrac{8}{5}\right)\)

2. Tìm x, biết:

a. \(1\dfrac{2}{5}x+\dfrac{3}{7}=\dfrac{4}{5}\)

b. |x - 1,5| = 2

c. \(\dfrac{4}{5}-\left|x-\dfrac{1}{6}\right|=\dfrac{2}{3}\)

d. 3^x . 2^x = 216

e. \(\dfrac{1}{2}\left(x-\dfrac{1}{3}\right)+\dfrac{-1}{2}=\dfrac{3}{4}\)

* Lm nhanh nha

Ths you <3

A=\(\dfrac{\left(12.8\right)^3.5}{2^9.15^2}\)

Bài 1: Tìm x, biết :

a, \(\dfrac{11}{13}\) - \((\dfrac{5}{42}\) - x \()\) = - \((\)\(\dfrac{15}{28}\)- \(\dfrac{11}{15}\)\()\)

b, \(|x+\dfrac{4}{15}|\) - \(|-3,75|\)= - \(\left|-2,15\right|\)

c, \(\dfrac{5}{3}\) - \(\left|x-\dfrac{3}{2}\right|\) = \(\dfrac{-1}{2}\)

d,\(\left(x-\dfrac{2}{3}\right)\). \(\left(2x-\dfrac{3}{2}\right)\) = 0

BÀi 3: Tìm x,y biết

a, \(\left(x^2-4\right)^2\)+ \(\left(x+2^{ }\right)\)\(^2\) = 0

b, \(\left(x-y^{ }\right)^2\) + \(\left|y+2\right|\) = 0

c, \(\left|x-y\right|\)+ \(\left|y+\dfrac{9}{25}\right|\)= 0

d, \(\left|\dfrac{1}{2}-\dfrac{1}{3}+x\right|\)= \(\left(-\dfrac{1}{4}\right)\)- \(\left|y\right|\)

Cho A = \(\left(\dfrac{1}{2^2}-1\right).\left(\dfrac{1}{3^2}-1\right).\left(\dfrac{1}{4^2}-1\right)...\left(\dfrac{1}{100^2}-1\right)\)

So sánh A với \(-\dfrac{1}{2}\)

Câu 1 : Tính và so sánh :

C = \(\left(1-\dfrac{2}{2.3}\right)\left(1-\dfrac{2}{3.4}\right)\left(1-\dfrac{2}{4.5}\right)...\left(1-\dfrac{2}{n\left(n+1\right)}\right)\) so sánh với \(\dfrac{2n+2}{3n}\)

- Please help me !!!

Bài 1. a, Cho A = \(\left(\dfrac{1}{2}-1\right)\left(\dfrac{1}{3}-1\right).....\left(\dfrac{1}{10}-1\right)\)

So sánh A với \(\dfrac{-1}{9}\)

Bài 2. Cho A = \(\left(\dfrac{1}{2}-1\right)\left(\dfrac{1}{3}-1\right)....\left(\dfrac{1}{2008}-1\right)\left(\dfrac{1}{2009}-1\right)\)

B = \(\left(-1\dfrac{1}{2}\right)\left(-1\dfrac{1}{3}\right)....\left(-1\dfrac{1}{2007}\right)\left(-1\dfrac{1}{2008}\right)\)

Tính A . B ?

Tìm giá trị nhỏ nhất của các biểu thức sau:

A=\(-a^2+3a+4\)

(x+2)(x-3)=5

Tính

\(\dfrac{0,8:\left(\dfrac{4}{5}.1,25\right)}{0,64-\dfrac{1}{25}}+\dfrac{\left(1,08-\dfrac{2}{25}\right):\dfrac{4}{7}}{\left(6\dfrac{5}{9}-3\dfrac{1}{4}\right).2\dfrac{2}{17}}+\left(1,2.0,5\right):\dfrac{4}{5}\)

tính B=1+\(\dfrac{1}{2}\)(1+2)+\(\dfrac{1}{3}\)(1+2+3)+...+\(\dfrac{1}{100}\)(1+2+3+4+..+100)

\(2\dfrac{1}{2}\) +\(\dfrac{4}{7}:\dfrac{-8}{9}\)

6-3 x \(\dfrac{1^3}{3^3}\)

\(\dfrac{2}{5}\) :3x=\(\dfrac{2}{3}\) : \(\dfrac{4}{5}\)

Với số nguyên dương n nào thì A _(n)= 20ⁿ +16ⁿ -3ⁿ -1 \(⋮\) 323

bài 1

\(a,D=\left(y^2+2\right)\left(y-4\right)-\left(2y^2+1\right)\left(\dfrac{1}{2}y-2\right)\)

vs y = -2/3 giúp mk vs <3

Tìm x

a, \(\left(2-x\right)\times\left(\dfrac{4}{5}-x\right)< 0\)

b, \(\left(x-\dfrac{3}{2}\right)\times\left(2\times x-1\right)>0\)

c, \(\left(x-\dfrac{4}{7}\right)\div\left(x+\dfrac{1}{2}\right)>0\)

d, \(\left(2\times x-5\right)\div\left(x+1\dfrac{3}{4}\right)< 0\)

Giúp mk với

Tìm x, biết:
a) x + \(\dfrac{3}{5}\) = \(\dfrac{4}{7}\)
b) x - \(\dfrac{5}{6}\) = \(\dfrac{1}{6}\)
c) \(\dfrac{-5}{7}\) - x = \(\dfrac{-9}{10}\)
d) \(\dfrac{5}{7}\) - x = 10
e) x : ( \(\dfrac{1}{9}\) - \(\dfrac{2}{5}\) ) = \(\dfrac{-1}{2}\)
f) ( \(\dfrac{-3}{5}\) + 1,25 ) x = \(\dfrac{1}{3}\)
g) \(\dfrac{1}{3}\)x + ( \(\dfrac{2}{3}\) - \(\dfrac{4}{9}\) ) = \(\dfrac{-3}{4}\)
Các bn giúp mk nhanh nha. Sáng mai mk phải nộp cho thầy r. Mk sẽ tick cho.

Chứng minh phân số sau tối giản: (n^3+5n+1)/(n^4+6n^2+n+5) (n thuộc N)

BT1: Tìm x, biết:

2) \(0,28-0,3:\left(50\%.x-1\dfrac{1}{3}\right)=-1\dfrac{2}{3}\)

\(A=\left(-\dfrac{3}{4}+\dfrac{2}{3}\right):\dfrac{5}{11}+\left(-\dfrac{1}{4}+\dfrac{1}{3}\right):\dfrac{5}{11}\)

\(\dfrac{\dfrac{3}{4}-\dfrac{3}{5}+\dfrac{3}{7}+\dfrac{3}{11}}{\dfrac{13}{4}-\dfrac{13}{5}+\dfrac{13}{7}+\dfrac{13}{11}}\)