Quadratic Relations and x-intercepts

Hello, I am new here and I would like to know if someone might be able to help me with a question I am having a problem with. It is from a homework assignment that I have already received a poor mark from but unfortunately my substitute teacher is an idiot and not explaining what I did wrong to me and my actual teacher won't be back for I don't know how long.

So with that said, I am suppose to, "state the equation of the quadratic relation for each graph and then convert it to standard form." I was able to do the first part but I am having problems understanding this one:

y = a(x + r)(x + s) (Headbang)

This thing I don't understand about this is how am I suppose to find the value for "a" I know it's probably something really simple but I just can't, for the life of me, get it.

(x,y) = (-4, -3)

r = 5

s = 1

Any help would be appreciated.

Thank you