:))) ủaaaaa 

Vui z?

:v gửi lời hỏi thăm vs Zero nhắ:'))

-.- ý cj là qua đọc tn ý 

Qua bên HĐ đi:))

\(\dfrac{x}{5}=\dfrac{y}{3}\\ \rightarrow\dfrac{x^2}{25}=\dfrac{y^2}{9}\\ \rightarrow\dfrac{x^2}{25}=\dfrac{y^2}{9}=\dfrac{x^2-y^2}{25-9}=\dfrac{4}{16}=\dfrac{1}{4}\\ \rightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-\dfrac{5}{2}\end{matrix}\right.\\\left[{}\begin{matrix}y=\dfrac{3}{2}\\y=-\dfrac{3}{2}\end{matrix}\right.\end{matrix}\right.\)

`(4x-8)-3=5`

`4x-8=5+3=8`

`4x=8+8=16`

`x=16:4=4`

~~~~~~~~

`8-(2x-4)=2`

`2x-4=8-2=6`

`2x=6+4=10`

`x=10:2=5`

~~~~~~~

`5-(3x-11)=1`

`3x-11=5-1=4`

`3x=4+11=15`

`x=15:3=5`

\(\left(1-\dfrac{1}{2^2}\right)\left(1-\dfrac{1}{3^2}\right)\left(1-\dfrac{1}{4^2}\right)\cdot\cdot\cdot\left(1-\dfrac{1}{100^2}\right)\\ =\left(1-\dfrac{1}{2}\right)\left(1+\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1+\dfrac{1}{3}\right)\cdot\cdot\cdot\left(1-\dfrac{1}{100}\right)\left(1+\dfrac{1}{100}\right)\\ =\dfrac{1}{2}\cdot\dfrac{3}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{99}{100}\cdot\dfrac{101}{100}\\ =\left(\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{99}{100}\right)\left(\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot...\cdot\dfrac{101}{100}\right)\\ =\dfrac{1\cdot2\cdot...\cdot99}{2\cdot3\cdot...\cdot100}\cdot\dfrac{3\cdot4\cdot...\cdot101}{2\cdot3\cdot...\cdot100}\)

`=(1*\cancel(2)*...*\cancel(99))/(\cancel(2)*\cancel(3)*...*100)*(\cancel(3)*\cancel(4)*...*101)/(2*\cancel(3)*...*\cancel(100))`

`=1/100*101/2`

`=101/200`

\(5⋮\left(x-1\right)\\ \rightarrow x-1\in U\left(5\right)\\ \rightarrow x-1\in\left\{\pm1;\pm5\right\}\\ \rightarrow\left[{}\begin{matrix}x-1=1\\x-1=5\\x-1=-1\\x-1=-5\end{matrix}\right.\\ \rightarrow\left[{}\begin{matrix}x=2\\x=6\\x=0\\x=-4\end{matrix}\right.\)

`@6x=-54`

`x=-54:6`

`x=-9`

`@-8x=-72`

`x=(-72):(-8)`

`x=-9`

`@-4x=-20`

`x=(-20):(-4)`

`x=-5`

`-9/13*(-4)/3`

`=(-9*(-4))/(13*3)`

`=(-3*(-4))/(13*1)`

`=12/13`