How do you complete the square to answer quadratic equations?

x2+6x-2 = 0

We use completing the square when the equation cannot be factorised. Begin by placing x2  in the brackets and halving the number in front of the x (also known as the coefficient of x) to form (x+3)2 . Now if we expanded the brackets and we would have x2 +6x+9. Since +9 is not part of the original equation we must subtract it giving (x+3) 2 -9. Returning to the original equation we must also -2 giving us (x+3)2-11

x2+6x-2 = (x+3)2 -11 = 0 so to solve, we treat like a normal equation. 
(x+3)2 = 11
(x+3) = √(11)
x=-3+/-√(11)

Answered by Mikhailia M. Maths tutor

3990 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Remove the brackets: −{−2[x−3(y−4)]−5(z+6)}


ABCDEFGH is a cuboid. AB=5.6 cm CH=7.2cm. Angle BCA=44degrees. Find the size of the angle between AH and the plane ABCD giving your answer correct to one dp.


Differentiate (x^2)*(e^x) using product rule


Factorise x² + 10x + 16


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