You are Here: Home >< Maths

# C1 - sketching a graph watch

1. Question: Sketch the graph of y=x^2-6x+3, giving the coordinates of the minimum point.

Since I can't factorise it normally, I used the quadratic formula and got 3+root6 or 3-root6. I'm not sure how to continue from here. Do I sub the values into the quadratic to find the value of y for each one? Then the minimum point is the one lowest in the graph?
2. (Original post by Student1914)
Question: Sketch the graph of y=x^2-6x+3, giving the coordinates of the minimum point.

Since I can't factorise it normally, I used the quadratic formula and got 3+root6 or 3-root6. I'm not sure how to continue from here. Do I sub the values into the quadratic to find the value of y for each one? Then the minimum point is the one lowest in the graph?
The x value of the minimum point is the mean of the two roots but this is a laborious way to find it. Do you know how to complete the square? This gives the coordinates of the minimum immediately.
3. (Original post by Mr M)
The x value of the minimum point is the mean of the two roots but this is a laborious way to find it. Do you know how to complete the square? This gives the coordinates of the minimum immediately.
Completing the square would give (x-3)^2 -6.
4. (Original post by Student1914)
Completing the square would give (x-3)^2 -6.
Yes so the coordinates of the minimum are (3, -6).

In general, when the minimum is .
5. (Original post by Mr M)
Yes so the coordinates of the minimum are (3, -6).

In general, when the minimum is .
6. (Original post by Student1914)
Completing the square gives the location of the maximum of a parabola too.

http://www.mathcentre.ac.uk/resource...re1-2009-1.pdf
7. (Original post by Mr M)
Completing the square gives the location of the maximum of a parabola too.

http://www.mathcentre.ac.uk/resource...re1-2009-1.pdf
Thanks!

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 11, 2017
Today on TSR

### Edexcel GCSE Maths Unofficial Markscheme

Find out how you've done here

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams