Who on another boring night

We just started the introduction into circles and i have no idea how to do this.

For problems 29 - 31 the graph of a quadratic function y=ax^2 + bx + c is shown. tell whether the discriminant of ax^2 + bx + c = 0 is positive, negative, or zero.

Which of the following pair(s) of circles have las a common external tangent? select all that apply. a and b a and c b and c