a) \(A=\left(5x-3\right)^2-2\left(5x-3\right)\left(x+3\right)+\left(x+3\right)^2\) ( \(5x-3\) chứ sao lại \(5x+3\) )

\(\Leftrightarrow A=\left[\left(5x-3\right)-\left(x+3\right)\right]^2\)

\(\Leftrightarrow A=\left(5x-3-x-3\right)^2\)

\(\Leftrightarrow A=\left(4x-6\right)^2\)

\(\Leftrightarrow A=\left(4x\right)^2-2.4x.6+6^2\)

\(\Leftrightarrow A=16x^2-48x+36\)

b) \(x^3+5x^2+6x\)

\(=x\left(x^2+5x+6\right)\)

\(=x\left(x^2+3x+2x+6\right)\)

\(=x\left[\left(x^2+3x\right)+\left(2x+6\right)\right]\)

\(=x\left[x\left(x+3\right)+2\left(x+3\right)\right]\)

\(=x\left(x+3\right)\left(x+2\right)\)

có lộn đề ko vậy

tích nha  Ngô Thượng Đăng

\(-1,53:\left(5\dfrac{5}{28}-1\dfrac{8}{9}.1,25+1\dfrac{16}{63}\right)\)

\(=-1,53:\left(5\dfrac{5}{28}-\dfrac{17}{9}.\dfrac{5}{4}+1\dfrac{16}{63}\right)\)

\(=-1,53:\left(5\dfrac{5}{28}-\dfrac{17.5}{9.4}+1\dfrac{16}{63}\right)\)

\(=-1,53:\left(5\dfrac{5}{28}-\dfrac{85}{36}+1\dfrac{16}{63}\right)\)

\(=-1,53:\left(\dfrac{145}{28}-\dfrac{85}{36}+\dfrac{79}{63}\right)\)

\(=-1,53:\left(\dfrac{1305}{252}-\dfrac{595}{252}+\dfrac{316}{252}\right)\)

\(=-1,53:\dfrac{1305-595+316}{252}\)

\(=-1,53:\dfrac{1026}{252}\)

\(=\dfrac{-153}{100}:\dfrac{57}{14}\)

\(=\dfrac{-153}{100}.\dfrac{14}{57}\)

\(=\dfrac{-153.14}{100.57}\)

\(=\dfrac{-2142}{5700}\)

\(=\dfrac{-357}{950}\)

này an ơi cái chỗ \(\Leftrightarrow x\sqrt{y}+y\sqrt{z}+z\sqrt{x}\le24\) mk ko hiểu

dễ mà!!!

phân tích ra pạn!!!

nếu hk bik lm thì tick đi r mình lm cho!!!

5609 

đúng thì bảo mình nhé

Bằng 33,1 bạn ạ , tick nha bạn thân !!!!

a) \(A=\dfrac{x^3-3x^2-x+3}{3x-x^2}\)

\(\Leftrightarrow A=\dfrac{x^3-3x^2-x+3}{-\left(x^2-3x\right)}\)

\(\Leftrightarrow A=\dfrac{\left(x^3-3x^2\right)-\left(x-3\right)}{-\left(x^2-3x\right)}\)

\(\Leftrightarrow A=\dfrac{x^2\left(x-3\right)-\left(x-3\right)}{-x\left(x-3\right)}\)

\(\Leftrightarrow A=\dfrac{\left(x-3\right)\left(x^2-1\right)}{-x\left(x-3\right)}\)

\(\Leftrightarrow A=\dfrac{x^2-1}{-x}\)

\(\Leftrightarrow A=\dfrac{-x^2+1}{x}\)

b) Để \(A\in Z\Leftrightarrow\dfrac{-x^2+1}{x}\in Z\Leftrightarrow-x^2+1⋮x\)

\(\Rightarrow1⋮x\)

\(\Rightarrow x\in U\left(1\right)=\left\{-1;1\right\}\)

\(\Rightarrow x\in\left\{-1;1\right\}\)

Vậy \(x=-1\) hoặc \(x=1\) thì \(A\in Z\)

 co : 

          14 / 21=14/21

           1=21/21