a: \(\left\{{}\begin{matrix}x-y=1\\2x-5y=-4\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}2x-2y=2\\2x-5y=-4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x-2y-2x+5y=2+4\\x-y=1\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}3y=6\\x-y=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=2\\x=y+1=3\end{matrix}\right.\)
b: \(\left(x+1\right)^2+2\cdot\left(x-1\right)=4\)
=>\(x^2+2x+1+2x-2-4=0\)
=>\(x^2+4x-5=0\)
=>(x+5)(x-1)=0
=>\(\left[{}\begin{matrix}x=-5\\x=1\end{matrix}\right.\)
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