Answer :
So it cuts the y axis at -9 as it has a gradient of 0.
Therefore y=-9 is the equation, as y=mx+c, it intercepts at -9 and has a gradient of 0, therefore y=0x-9 so y=-9.
Therefore y=-9 is the equation, as y=mx+c, it intercepts at -9 and has a gradient of 0, therefore y=0x-9 so y=-9.
