Use completing the square to find the minimum of y = x^2 - 4x + 8

Remember completing the square gives a result of the form (x+q)2 + p where q and p are numbers
Also q is always half of the x term, which in this case is -4, as such q = -2
Substituting this in, we get (x-2)2 which expands to x2 - 4x + 4. To make this equal to our original equation, we need to add 4, getting us y = (x-2)2 + 4.
As a rule, the minimum point is always x = -q, y = p. Therefore our answer is (2,4)

SD
Answered by Sol D. Maths tutor

2859 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Simplify (2sin45 - tan45)/(4tan60) and leave your answer in the form of (sqrt(a)-sqrt(b))/c


Show that (x + 1)(x + 2)(x + 3) can be written in the form ax3 + bx2 + cx + d where a, b, c and d are positive integers.


Factorise 15r+10


expand and simplify (x+3)(x-7)


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