Coordinate Geometry - GMAT Prep EX.

[Margreter]

In the xy plane, at what 2 points does the graph y= (x+a)(x+b) intercect the x-axis?

a) a+b =-1
b) THe graph intersect Y at (0, -6)

The answer i C)....but how come? Do not understand what A is all about...

Thanks for all your help!