Core 1 – discriminant

Yesterday we looked at solving inequalities. This topic is often combined with use of the discriminant. The discriminant (D = b2 – 4ac) tells you how many roots a quadratic of the form ax2 + bx + c = 0 has.

if

D > 0, there are two distinct and real roots

D = 0, there is one repeated root

D < 0, there are no real roots

 

Watch the video below and then try the exam questions

January 2006 question 4 – answers here

June 2013 question 7 – answer here

Most question though are harder than this, take a look through some of these videos and then try the exam question below.

January 2013 Question 8 – answer here

Core 1 – Quadratic Inequalities

This topic is something that students often get wrong. The main thing to note is that it is really helpful to draw a graph. If the question is an inequality then it is likely that the answer will be an inequality.

These kind of questions almost always come up with the discriminant, which will be tomorrow’s lesson. For the moment just try the part questions below and we’ll look at whole questions next time.

January 2006 Question 8d – answer here

January 2008 Question 7c – answer here