How do you complete the square?

Say you start with a general equation of x2+ax+b=0. (If the x2 has a coefficient the you will need to divide by that first.)

You need to move to the equation (x+a/2)2 -(a/2)2+b=0. Then put all of the constants together on the other side and square root everything so you end up with x-a/2 equalling plus or minus the square root of (a/2)2-b. You can then move to x equalling a/2 plus or minus the square root of (a/2)2-b.

For example, x2+6x+2=0 --> (x+3)2-32+2 =0 --> (x+3)2 =7 --> x+3 =+/-sqrt(7) --> x=-3+/-sqrt(7)

BC
Answered by Bryony C. Maths tutor

2705 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

There are 200 students in Year 10 110 are boys. There are 250 students in Year 11 140 are boys. Which year has the greater proportion of boys? (Taken from Nov 2014 AQA Unit 2)


Rearrange the following making a the subject: (a+2)/5 = 3a+b


How do I find the missing length using trigonometry?


What is the best way to prepare to sit my exams?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences