1) x2+3x-4=x2+4x-x-4=(x2-x)+(4x-4)=x(x-1)+4(x-1)=(x-1)(x+4)
1: Ta có: \(x^2+3x-4=0\)
\(\Leftrightarrow\left(x+4\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=1\end{matrix}\right.\)
2: Ta có: \(x^2-7x-8=0\)
\(\Leftrightarrow\left(x-8\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-1\end{matrix}\right.\)
3: Ta có: \(x^2+4x-5=0\)
\(\Leftrightarrow\left(x+5\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-5\\x=1\end{matrix}\right.\)
4: Ta có: \(3x^2-5x+2=0\)
\(\Leftrightarrow\left(x-1\right)\left(3x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{2}{3}\end{matrix}\right.\)
5: Ta có: \(4x^2-7x+3=0\)
\(\Leftrightarrow\left(x-1\right)\left(4x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{3}{4}\end{matrix}\right.\)