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

x2 + 8x = (x + 4)2 - 16, so x2 + 8x - 5 = (x + 4)2 - 16 - 5 = (x + 4)2 - 21, so then (x + 4)- 21 = 0 (x + 4)= 21 -----> x + 4 = √21 -------> x = -4 + √21                               x = -4 - √21

SJ
Answered by Shadab J. Maths tutor

11365 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

x^2-x-12


Consider f:R -> R, f = x/ sqrt(x^2+1). Prove that for any a between -1 and 1, f(x)=a has only one solution.


How do I expand a factorised expression?


There is a right angled triangle with sides of 5cm, 12cm and 13cm. What is the size of the smallest angle?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning