perpendicular means that the slope should be -1/4 (in respect to original slope of 4) so then u have the equation: $y = -\frac{ 1 }{ 4 }x + c$ then you plug in y for 7 and x for 0 so you get $7 = -\frac{ 1 }{ 4 }0 + c$ so then c = 7... which makes your function $y = -\frac{ 1 }{ 4 }x + 7$