I think what we're trying to do here is put the equation in y=mx+b form.

So first thing I would do before moving to the statements is to expand the (x+a)(x+b)

= x^2+ax+bx+ab
= x^2+(a+b)x+ab

Now, let's move onto our statements with the goal of finding (a+b) AND ab.

St 1) a+b =-1

- Tempting, but this gives us only one of our unknowns, not both so INSUFF

St 2) (0,-6) is a point on the graph

- so let's plug this point into our expanded formula

y = x^2+(a+b)x+ab
(-6) = 0^2 + (a+b)*(0) +ab
(-6) = ab

- again, tempting, but we don't know a+b from this equation, so INSUFF

Bringing the two together gives us both unknowns a+b AND ab

So answer C.