a, \(\sqrt{x^2-6x+9}=2\)

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

\(\Leftrightarrow\left|x-3\right|=2\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=2\\x-3=-2\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=1\end{matrix}\right.\)

a: Ta có: \(\sqrt{x^2-6x+9}=2\)

\(\Leftrightarrow\left(x-5\right)\left(x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=1\end{matrix}\right.\)

\(pt\Leftrightarrow\left|x-3\right|=3-x\)

*)xét x>=3

*)Xét x<3

dễ nhé

Bài 1: 

1: 

a: \(\sqrt{12}+3\sqrt{48}-5\sqrt{75}\)

\(=2\sqrt{3}+12\sqrt{3}-25\sqrt{3}\)

\(=-11\sqrt{3}\)

mới líp 6 mừ

bạn lớp mấy

a: Ta có: \(\sqrt{x^2-4x+4}=\sqrt{4x^2-12x+9}\)

\(\Leftrightarrow\left|x-2\right|=\left|2x-3\right|\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-3=x-2\\2x-3=2-x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{5}{3}\end{matrix}\right.\)

c: Ta có: \(\sqrt{4x^2-4x+1}=\sqrt{x^2-6x+9}\)

\(\Leftrightarrow\left|2x-1\right|=\left|x-3\right|\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=x-3\\2x-1=3-x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{4}{3}\end{matrix}\right.\)

Câu 2.2 

để 2 đt song song khi \(\left\{{}\begin{matrix}m^2-1=3\\m+1\ne3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m^2=4\\m\ne2\end{matrix}\right.\Leftrightarrow m=2\)

Câu 2: 

1: \(A=\left(\sqrt{x}+\sqrt{y}-\sqrt{x}+\sqrt{y}-y\right)\cdot\left(\sqrt{y}-2\right)\)

\(=\left(2\sqrt{y}-y\right)\left(\sqrt{y}-2\right)=-\sqrt{y}\left(y-4\sqrt{y}+4\right)=-y\sqrt{y}+4y-4\sqrt{y}\)