[tex]\boxed{\begin{array}{l}\rm~gr\acute afico~vermelho: passa~pelos~pontos~A(0,-2)~B(3,1)\\\sf a=\dfrac {1-[-2]}{3-0}=\dfrac{3}{3}=1\\\sf f(x)=ax+b\\\sf f(0)=a\cdot 0+b\\\sf b=-2\\\sf f(x)=x-2\\\sf y=x-2\end{array}}[/tex]
[tex]\boxed{\begin{array}{l}\rm gr\acute afico~azul:passa~pelos~pontos~B(3,1)~e~C(0,4). \\\sf a=\dfrac{4-1}{0-3}=\dfrac{3}{-3}=-1\\\sf g(x)=ax+b\\\sf g(0)=a\cdot 0+b\\\sf b=4\\\sf g(x)=-x+4\\\sf y=-x+4 \end{array}}[/tex]
[tex]\Large\boxed{\begin{array}{l}\rm o~sistema~pedido~\acute e\\\begin{cases}\sf y=x-2\\\sf y=-x+4\end{cases}\end{array}}\blue{\checkmark}[/tex]
