$d: y=ax+b // y=\dfrac{1}{2}x$
$\Rightarrow a=\dfrac{1}{2}; b\ne 0$
Hoành độ điểm đi qua $d$:
$-\dfrac{1}{2}x+1=3x+5$
$\Leftrightarrow x=\dfrac{-8}{7}$
$\Rightarrow y=\dfrac{11}{7}$
Thay vào $d$:
$\dfrac{1}{2}.\dfrac{-8}{7}+b=\dfrac{11}{7}$
$\Leftrightarrow b=\dfrac{15}{7}$ (TM)
Vậy $d: y=\dfrac{1}{2}x+\dfrac{15}{7}$