Đáp án là: D

để pt được xác định thì :

\(x-2\ne0;x^2-1\ne0\)

=>\(\left\{{}\begin{matrix}x\ne2\\x\ne-1\\x\ne1\end{matrix}\right.\)

Vậy chọn B

a) Ta có: \(\left(2x+3\right)^2-4\left(x-2\right)\left(x+2\right)\)

\(=4x^2+12x+9-4\left(x^2-4\right)\)

\(=4x^2+12x+9-4x^2+16\)

\(=12x+25\)

b) Ta có: \(\dfrac{x+6}{x^2-4}-\dfrac{2}{x\left(x+2\right)}\)

\(=\dfrac{x\left(x+6\right)}{x\left(x+2\right)\left(x-2\right)}-\dfrac{2\left(x-2\right)}{x\left(x+2\right)\left(x-2\right)}\)

\(=\dfrac{x^2+6x-2x+4}{x\left(x+2\right)\left(x-2\right)}\)

\(=\dfrac{x^2+4x+4}{x\left(x+2\right)\left(x-2\right)}\)

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

\(=\dfrac{x+2}{x\left(x-2\right)}\)

     2 câu thôi nhé!!!

b.\(x-2\sqrt{x}=\sqrt{x}\left(\sqrt{x}-2\right)\) 

c.\(\sqrt{x}-3x=\sqrt{x}\left(1-3\sqrt{x}\right)\)

1.

7x(2x-1)=14x²-7x

2

a. x²+2x=x(x+2)

b.x²-xy+3x-3y

=x(x-y)+3(x-y)

=(x+3)(x-y)

Câu 2:

 1. 2x/2x-5 -  5/2x-5

=2x-5/2x-5

=1

2. (6x³-7x²-x+2) : (x-1)=6x²-x-2

a: Ta có: \(x^2-2x=0\)

\(\Leftrightarrow x\left(x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\end{matrix}\right.\)

b: Ta có: \(\left(x-1\right)\cdot x-2\left(1-x\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(x+2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-2\end{matrix}\right.\)

c: Ta có: \(x^3+2x^2+x=0\)

\(\Leftrightarrow x\left(x+1\right)^2=0\)

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

d: Ta có: \(x^3-3x^2=0\)

\(\Leftrightarrow x^2\left(x-3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)