2015 · Q40
The sign of the quadratic polynomial ax²+bx+c is always positive if
Elementary MathematicsAlgebra
- Aa is positive and b² -4ac
- Ba is positive and b² -4ac
- Ca can be any real number and b² -4ac
- Da can be any real number and b² - 4ac > 0
Explanation
ax²+bx+c > 0 for all real x iff the parabola opens upward (a > 0) and never touches zero, i.e. discriminant b² − 4ac < 0 (option A; the option text is truncated in the source, but this is the standard condition).