急!!!!!二次函數mc題

the graph y=ax^2+bx+c and a straight line y=-bx-3c intersect at a point and y=ax^2+bx+c ,where a is positive, and does not touch the x-axis ,which one is true ?

I think this questions have some problem:
First, y=ax^2+bx+c and y=-bx-3c intersect at a point
then we have
-bx-3c=ax^2+bx+c have real roots
ax^2+2bx+4c=0 have real roots
so
delta = (2b)^2-4(a)(4c) > (or eq. to)0
After simplify,
we get
b^2-4ac >(or eq. to) 0

but y=ax^2+bx+c does not touch the x-axis
implies we have
delta = b^2 - 4ac <0, which is a contradiction

but if you mean y=ax^2+bx+c呢條式唔同x-axis"相交" [make sure touch =/= 相交]
then we can have delta = b^2 - 4ac <(or eq. to)0
thus we have
b^2-4ac=0

And I don't understand what you mean by when f(0)?