Find the minimum value of the quadratic 3x^2-8x+1.

This is a question about completing the square. The first step involves taking the factor of 3 our of the expression to reach the correct form for completing the square to reach 3(x^2-(8/3)x)+1. Then, consider x^2-(8/3)x and complete the square of this expression. The coefficient of x is -(8/3) so half of that is -(4/3) so we get (x-(4/3))^2-(16/9). We now substitute this back into the expression before so we have 3x^2-8x+1=3(x^2-(8/3)x)+1=3((x-(4/3))^2-(16/9))+1=3(x-(4/3))^2-(16/3)+1=3(x-(4/3))^2-(13/3)and this is in the correct form for completing the square. To find the minimum value we simply have to notice that the smallest value the squared term can be is 0 so the minimum value of the whole expression is -(13/3).

JM
Answered by Jamie M. Maths tutor

3367 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Solve the simultaneous equations: (1) 4x + y = 7 and (2) x - 3y = 5


Rewrite in the logarithmic form: T=2π√(L/G)


There are only 7 blue pens, 4 green pens and 6 red pens in a box. One pen is taken at random from the box. Write down the probability that this pen is blue.


How to recognise and make the link between probability and the algebraic demands of this question?


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:

© 2026 by IXL Learning