Bài 9A:

\(a,\left(x+5\right)^2-\left(x-5\right)^2-2x+1=0\\ \Leftrightarrow\left(x^2+10x+25\right)-\left(x^2-10x+25\right)-2x+1=0\\ \Leftrightarrow x^2-x^2+10x+10x-2x=-1-25+25\\ \Leftrightarrow18x=-1\\ \Leftrightarrow x=-\dfrac{1}{18}\\ b,\left(2x-7\right)^2-\left(x+3\right)^2=3x^2+6\\ \Leftrightarrow4x^2-28x+49-x^2-6x-9-3x^2-6=0\\ \Leftrightarrow4x^2-x^2-3x^2-28x-6x=6+9-49\\ \Leftrightarrow22x=-34\\ \Leftrightarrow x=-\dfrac{17}{11}\\ c,\left(3x+2\right)^2-9\left(x-5\right)\left(x+5\right)=225-5x\\ \Leftrightarrow9x^2+12x+4-9\left(x^2-25\right)=225-5x\\ \Leftrightarrow9x^2-9x^2+12x+5x=225-4+9.25\\ \Leftrightarrow17x=446\\ \Leftrightarrow x=\dfrac{446}{17}\)

Sao bài này câu nào x cũng k nguyên ta, hơi xấu hi

9B

\(a,\left(4x-1\right)^2-4\left(2x-3\right)^2-x-4=0\\ \Leftrightarrow16x^2-8x+1-4\left(4x^2-12x+9\right)-x-4=0\\ \Leftrightarrow16x^2-16x^2-8x+48x-x=4+36-1\\ \Leftrightarrow39x=39\\ \Leftrightarrow x=1\\ b,x\left(x-5\right)-\left(4-x\right)^2=7x+1\\ \Leftrightarrow x^2-5x-\left(16-8x+x^2\right)-7x-1=0\\ \Leftrightarrow x^2-x^2-5x+8x-7x=1+16\\ \Leftrightarrow-4x=17\\ \Leftrightarrow x=\dfrac{-17}{4}\\ c,\left(2x-6\right)\left(x+3\right)=2\left(x-3\right)^2\\ \Leftrightarrow2x^2-6x+6x-18=2\left(x^2-6x+9\right)\\ \Leftrightarrow2x^2-2x^2-6x+6x+12x=18+18\\ \Leftrightarrow12x=36\\ \Leftrightarrow x=\dfrac{36}{12}=3\)

(\(x+1\))² - (\(x+1\)) = 0

(\(x+1\))(\(x+1-1\)) =0 

(\(x+1\))\(x\)   = 0

\(\left[{}\begin{matrix}x+1=0\\x=0\end{matrix}\right.\)

\(\left[{}\begin{matrix}x=-1\\x=0\end{matrix}\right.\)

Vậy \(x\in\){ -1; 0}

Giải bằng cách phân tích đa thức thành nhân tử nhé mn

345(789)432):--:  ...

\(D=\left(x^2-1\right)^3-\left(x^4+x^2+1\right)\left(x^2-1\right)\)

\(\Rightarrow D=x^6-3x^4+3x^2-1-\left(x^6-1\right)\)

\(\Rightarrow D=-3x^4+3x^2=3x^2\left(1-x^2\right)\)

\(1\dfrac{1}{2}\times1\dfrac{1}{3}\times...\times1\dfrac{1}{99}=\dfrac{3}{2}\times\dfrac{4}{3}\times...\times\dfrac{100}{99}=\dfrac{100}{2}=50\)

` a/`

` 2 - 1 5/6 + 2 2/3 = 2 - 11/6 - 8/3 = 1/6+ 8/3 = 1/6 + 16/6 = 17/6 `

`b/`

`5/9 xx ( 2 5/6 - 1 2/3 ) = 5/9 xx ( 17/6 - 5/3 ) = 5/9 xx 7/6 = 35/54 `

`c/` 

`1 1/3 : ( 2 + 1 1/6 : 2 5/6 ) `

`= 4/3 : ( 2 + 7/6 xx 6/17 ) `

`= 4/3 : ( 2 + 7/17 ) `

`= 4/3 : 41/17 `

`= 4/3 xx 17/41 `

`= 86/123`

` d/` 

` 2 3/5 : 3/4 xx 1 4/5 = 13/5 xx 4/3 xx 9/5 =52/15 xx 9/5 = 156/25`

\(a,2\dfrac{3}{4}-a+\dfrac{1}{4}=1\dfrac{1}{2}\\ \Leftrightarrow a=\dfrac{3}{2}\\ b,3\dfrac{1}{4}-a-1\dfrac{3}{4}=\dfrac{7}{9}\\ \Leftrightarrow a=\dfrac{13}{18}\\ c,2\dfrac{5}{6}-1\dfrac{1}{2}-a=\dfrac{1}{6}\\ \Leftrightarrow a=\dfrac{7}{6}\)

mình không bieets làm

\(10⋮\left(x+5\right)\)

\(\Rightarrow x+5\in\left\{-1;1;-2;2;-5;5;-10;10\right\}\)

\(\Rightarrow x\in\left\{-6;-4;-7;-3;-10;0;-15;5\right\}\left(x\in Z\right)\)

Để 10 ⋮ (x+5) thì (x+5) ∈ Ư(10)

⇒ (x+5) ∈ \(\left\{\pm1;\pm2;\pm5;\pm10\right\}\)

⇒ x ∈ {5;0;-3;-4;-6;-7;-10;-15}

\(b,\left(5x-1\right)^2:2=8\\ \Leftrightarrow\left(5x-1\right)^2=16\\ \Leftrightarrow\left[{}\begin{matrix}5x-1=4\\5x-1=-4\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{3}{5}\end{matrix}\right.\\ c,\left(1-3x\right)^3=-64\\ \Leftrightarrow1-3x=-4\\ \Leftrightarrow3x=5\\ \Leftrightarrow x=\dfrac{5}{3}\)