# What you need to know for O Level for Quadratic Functions (O Level Add Maths) In O Level Additional Mathematics, this is what you need to know for quadratic functions:

• Finding maximum and minimum of a quadratic function by completing the square
• i.e. converting ax2 + bx + c to a(x+h)2 + g
• Conditions for a quadratic function to be always positive or negative
• Using results from completing the square i.e. ax2 + bx + c = a(x+h)2 + g
• This occurs when a > 0 and g > 0
• This occurs when  a < 0 and g < 0
•  Using discriminant (b2– 4ac) to find the conditions where a quadratic equation has:
• no real roots ==> b2– 4ac < 0
• 2 distinct real roots ==> b2– 4ac > 0
• equal roots ==> b2– 4ac = 0
• Using discriminant (b2– 4ac) to find the conditions where a line is:
• tangent to a quadratic curve ==> b2– 4ac > 0
• cuts a quadratic curve at 2 distinct points ==> b2– 4ac > 0
• does not intersect the quadratic curve ==> b2– 4ac < 0
• Solving simultaneous equations
• This can be done using the substitution method (most commonly used) or the elimination method.