How do I solve a quadratic equation by competing the square?

How would you solve  x2+8x+16=81Show that this can be factorised (x+4)2=92Which can then be easily solved by square rooting both sides
What if we could now use this method to solve all quadratics?!!?
Consider Solve  x2+6x+1=0
We can complete the square by:(x+3)2-9+1=0 (x+3)2-8=0 (x+3)2=8 (x+3)=±√8 x=-3±2√2

Answered by Maths tutor

3445 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

What is 90 million in standard form?


Solve the following simultaneous equation: y= x^2 - 3x + 4 y - x = 1


Calculate the area of a circle where the circumference of the circle and sides of the square are tangential at 4 points.


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


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:

© 2026 by IXL Learning