\(a,xy+y^2-x-y=y\left(x+y\right)-\left(x+y\right)=\left(y-1\right)\left(x+y\right)\)\(b,25-x^2+2xy-y^2=25-\left(x-y\right)^2=\left(5-x+y\right)\left(5+x-y\right)\)Bài 2:
\(x\left(x-2\right)+\left(x-2\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
b, \(\left(2x-1\right)^2-\left(x+3\right)^2=0\)
\(\Leftrightarrow\left(2x-1-x-3\right)\left(2x-1+x+3\right)=0\)
\(\Leftrightarrow\left(x-4\right)\left(3x+2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-4=0\\3x+2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-\dfrac{2}{3}\end{matrix}\right.\)
