msierra
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# Estimate the solution of the linear system graphically x+y=6 x-y=12

$\left\{\begin{array}{ccc}x+y=6\\x-y=12\end{array}\right\\\left\{\begin{array}{ccc}y=-x+6\\y=x-12\end{array}\right\\\\y=-x+6\\for\ x=0\to y=-0+6=6\to(0;\ 6)\\for\ x=6\to y=-6+6=0\to(6;\ 0)\\\\y=x-12\\for\ x=6\to y=6-12=-6\to(6;-6)\\for\ x=12\to y=12-12=0\to(12;\ 0)\\\\\left\{\begin{array}{ccc}x=9\\y=-3\end{array}\right$