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 ▸

Show that the square of any odd integer is of the form (8k+1)


Solve the second order ODE, giving a general solution: x'' + 2x' - 3x = 2e^-t


A tank contains 500L of salty water. Pure water is pumped in at a rate of 10 L/sec, and the the mixture is pumped out at a rate of 15L/ sec. If the concentration of salt is 5g/L initially, form an equation of amount of salt, s, at t seconds.


When and how do I use proof by induction?


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