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

3107 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Solve 3x-8=19


To make 12 cakes you need 100g of butter, 6 eggs, and 40g of sugar. How many cakes can you make with 450g of butter, 15 eggs, and 110g of sugar?


Find the inverse of f(x) = 7x+4


Solve algebraically: 6a+b=16, 5a-2b=19


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