Question

Answer 1

Tọa độ giao điểm của y+2x-1=0 và y=x+7 là:

\(\left\{{}\begin{matrix}y=x+7\\y+2x=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x-y=7\\2x+y=1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}3x=8\\x-y=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{8}{3}\\y=x-7=-\dfrac{13}{3}\end{matrix}\right.\)

Thay \(x=\dfrac{8}{3};y=-\dfrac{13}{3}\) vào \(y=\left(m-1\right)x-m+3\), ta được:

\(\dfrac{8}{3}\left(m-1\right)-m+3=-\dfrac{13}{3}\)

\(\Leftrightarrow\dfrac{8}{3}m-\dfrac{8}{3}-m+3=-\dfrac{13}{3}\)

\(\Leftrightarrow m\cdot\dfrac{5}{3}=-\dfrac{14}{3}\)

hay \(m=-\dfrac{14}{5}\)