Solve x^2+8x-5=0 using completing the square

by completing the square we write the equation as (x+b/2)^2-b/2^2+c, in this case b=8 (the coefficient of x) and c=5 so we have (x+4)^2-16-5=0, which equals (x+4)^2-21=0. Now by rearranging we get (x+4)^2=21, which goes to x+4=+or-sqrt(21). Therefore x=sgrt21 -4 or x=-sqrt21 -4

Related Further Mathematics A Level answers

All answers ▸

Prove that sum(k) from 0 to n is n(n+1)/2, by induction


How do I express complex numbers in the form reiθ?


A line has Cartesian equations x−p = (y+2)/q = 3−z and a plane has equation r ∙ [1,−1,−2] = −3. In the case where the angle θ between the line and the plane satisfies sin⁡θ=1/√6 and the line intersects the plane at z = 0. Find p and q.


Find the set of values of x for which (x+4) > 2/(x+3)


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