(1) B 2-4ac = 0 because there is only one intersection.

Because b+ac=3, AC = 3-B.

(b-2) (b+6) of simultaneous expression = 0.

B=2 or b=-6.

Because the parabola axis of symmetry is -b/2a, it can be seen from the figure that this value is greater than 0.

And because a<0 (open down)

So b=2.

(2)p(- 1/a，0)，q(0，c)

Principle of triangle area equality (-1/a)*(-c)=pq*oa

Where pq can be calculated from the p and q coordinates,

The above formula can be simplified as 2+2 (AC) 2 = c 2.

Ac= 1 from b 2-4ac = 0.

So c=-2

So a=- 1/2.

I hope it will be helpful and adopted.