The line L passes through the points A(1,3) and B(-19,-19). Find an equation of L in the form ax+by+c=0.

So the answer in the back of the book is: 11x-10y+19=0

But when I do it:

Gradient = y2-y1/x2-x1

= -19-3/-19-1

= -16/-18

= 16/18

= 8/9

C =

y=8/9x+c

3=8/9x+c

c=3-8/9

c=27/9-8/9

c=19/9

y=8/9x+19/9

so 8/9x-y+19/9=0

so 8x-9y+19=0

So where did I go wrong?

Im guessing either a stupid mistake in there or the answer in the back of the book is wrong.