me assume the Quesshun is bout a strate line that go thru point=(-1,-4)
line: 2x-7y=-21
or 7y=2x+21, become y=(2/7)x +3
thur, slope=2/7
Projekt from point=(-1,-4) tu x=0...deltax=+1
deltay=slope*deltax=(2/7)
Thus, y at x=0 must be -4+(2/7)=(2-28)/7=-26/7
so line be y=(2/7)x-26/7