Sorry about my last post, i put the working out for a differnt question and i dont know how to delete the question.

This is the real working out..

Find the equation of the following straight line

through (0,-1) and ( 2, -9)

-9-1 / 2-0 = -10/2

y=10/2x + c

x = 0 y = -1

-1 = -10/2 (0) + c

giving c = -1

my answer y = -10/2x - 1

but the answer is y = -4x - 1

What am i doing wrong?