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)

Answered by Sol D. Maths tutor

2851 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Find the equation of the tangent to the curve y = x√x at the point (4,6).


A line passes through the points (-2,1) and (4,4). Find the equation of the line in the form y = mx + c


How do I expand (x-2)(3x+3) into a quadratic?


Solve the following ((3x + 1)/2x ) = 4


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