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

2763 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Work out the number of green pens in the box. (rest of Q below)


A ten-sided die with sides numbered 1-10 is thrown. What is the probability of throwing a 1?


How do I divide fractions?


Solve the simultaneous equations: 5x + y = 21, x - 3y = 9


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences