Ta giải Hpt \(\left\{{}\begin{matrix}y=2x-5\\y=x+2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x-y=5\\x-y=-2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x-y=5\\2x-2y=-4\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-y=-2\\y=9\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=7\\y=9\end{matrix}\right.\)
\(\Rightarrow\left(d_1\right)\cap\left(d_2\right)=A\left(7;9\right)\)
Thay \(A\left(7;9\right)\) vào \(\left(d_3\right):y=ax-12\)
\(\Leftrightarrow9=7a-12\)
\(\Leftrightarrow7a=21\)
\(\Leftrightarrow a=3\)
Vậy khi \(a=3\) thì \(\left(d_1\right);\left(d_2\right);\left(d_3\right)\) đồng quy tại \(A\left(7;9\right)\)
làm hộ mik bài 1 thôi nha
