Is it true that, if b>a+c>0, then the quadratic equation ax2+bx+c=0 has two roots?
A convex figure and point A inside it are given. Prove that there is a chord (that is, a segment joining two boundary points of a convex figure) passing through point A and dividing it in half at point A.
The expression ax2+bx+c is an exact fourth power for all integers x. Prove that a=b=0.