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

3372 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

What term comes next in the sequence: 5, 8, 11, 14


How to find the longest side of a right-angled triangle if we are given the two other sides?


Robin and Emma both buy cupcakes for a bake sale. Between them, they purchase 125 cupcakes for the bake sale. Emma buys 50% more cupcakes then Robin and gets a 20% discount. The total cost of the 125 cupcakes was £137.5. What is the price of one cupcake?


Find x when: (2^x)(e^(3x+1))=10. Give your answer in the form (a + ln(b)) / (c + ln(d)) , where a,b,c,d are integers.


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