The line passing through (1,y) and (3,0) is perpendicular to the line joining (5,3) and left parenthesis negative 1 comma 1 right parenthesis . find y.

We have that
The line passing through (1,y) and (3,0) is perpendicular to the line joining (5,3) and (-1,1)

step 1
find the slope of the line joining (5,3) and (-1,1)

slope m=(y2-y1)/(x2-x1)> m=(1-3)/(-1-5)---> m=-2/-6---> m=1/3

step 2
if two lines are perpendicular
the slopes
m1*m2=-1
m1=1/3
m2=-3
so
The line passing through (1,y) and (3,0) has a slope m2=-3
m2=(y2-y1)/(x2-x1)> m2=(0-y)/(3-1)> -y/2
-3=-y/2> y=6

the answer is
y=6

Cthe residual plot for model 1 has a non random pattern and is a good fit for the data