How do you solve an equation by completing the square?

Firstly, you can only complete the square on quadratic functions (functions in the form Ax2+Bx+C)

If A=1,

Consider B, the coefficient of x. Substitute it into ( x + (B/2) )2

We know if we multiply this out, we will get x2+Bx+(B/2)2

However, we want x2+Bx+C. 

We therefore subtract the (B/2)2 we don't want and add the C we do. 

This gives us ( x + (B/2) )2 - (B/2)2 + C. 

This method is called 'completing the sqaure'

If A does not = 1, manipulate the quadratic so it is in the form A( x+ (B/A) x + (C/A))Solve the bracket as normal and multiply through by A at the end.

 

 

EJ
Answered by Emma J. Maths tutor

4764 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

A circle, C, has an equation: x^2 + y^2 - 4x + 10y = 7 . Find the centre of the circle and its radius?


Solve x^2=3(x-1)^2


Differentiate with respect to x: y=2^x


How can we calculate the derivative of function f(x)= (x+2)/(x-1)?


We're here to help

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

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences