Question

Find the equation of a line that is parallel to the line y=x and contains the point (1,-9)

Answer 1

Y=mx+b

y=-9
x=1
m=?

slope of y=x is 1 and so m must equal -1 because the slope is negated and flipped.
so after finding that b=-8
y=-x-8

Answer 2

Eq. of line parallel to y=x is
y=x+c
∵it passes through (1,-9)
-9=1+c
c=-9-1=-10
so reqd. line is y=x-10