If ab>0 and bc<0, then ax^2+bx+c=0 has two real solutions. (Prove this)
I started, but I don't know.
Let a, b, c be real.
Assume ab>0 and bc<0.
I don't know from here. It clearly involves showing that the discriminant, b^2-4ac is positive I would think. How I can go about doing so, not sure.
Thanks for the help.