Factorise x^2+6x+5=0 by completing the square.

When completing the square, we first divide the whole equation by the x^2 component. In this case, the x^2 component is 1 so nothing changes. We now apply the method to convert to square form: we reduce the power of x in x^2 and 6x, and half 6x before putting them in brackets to the power 2, i.e [x^(2-1)+(6/2)x^(1-1)]^2. Remember, x^0=1. This simplifies to (x+3)^2. But, if we were to expand these brackets, we would get x^2+6x+9, which is 4 more than x^2+6x+5, so we take away 4. Therefore, our answer in completed square form is (x+3)^2-4=0.

Answered by Jonny I. Maths tutor

7901 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Factorise x^2+6x+8


How do you expand brackets?


A ladder 5m long is leaning up against a wall. The foot of the ladder is 3m from the wall. How high up the wall does the ladder reach?


A ladder of length 4.5m is leaning against a wall. The foot of the ladder is 2.3m from the base of the wall. What is the angle the ladder makes with the wall?


We're here to help

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