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

3046 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

5 tins of soup have a total weight of 1750 grams. 4 tins of soup and 3 packets of soup have a total weight of 1490 grams. Work out the total weight of 3 tins of soup and 2 packets of soup.


f(x) = 3x - 2a || g(x) = 2ax + 1 || fg(x) = 2x + b/2


The area of a rectangle is 8cm^2. It has a length of (3x+1)cm and a width of (2x+5)cm. Work out the value of x.


When do I use Sin, Cos and Tan?


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