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# Maths parabola minimum point? Watch

1. Hi,
I am a GCSE maths student, and I need some help with a parabola minimum point question I was doing for revision.
When a question asks 'find the minimum point' and gives you the equation of the parabola, what do you do after you complete the square?

For example, the question used the equation x squared - 8x +23

I then wrote this out as (x-4) squared + 7

Does this mean that y=7 and x=-4 ? Or do I put it into the first equation?
2. (Original post by katesimpson2112)
Hi,
I am a GCSE maths student, and I need some help with a parabola minimum point question I was doing for revision.
When a question asks 'find the minimum point' and gives you the equation of the parabola, what do you do after you complete the square?

For example, the question used the equation x squared - 8x +23

I then wrote this out as (x-4) squared + 7

Does this mean that y=7 and x=-4 ? Or do I put it into the first equation?
Almost, check the sign on your x-value.

The smallest value (x-4)2 can take is zero, since squared numbers are always positive. So you can immediately see that the minimum point, y=7, will be where the squared bracket is zero, i.e: where x-4=0.

3. So do you mean that:
If x-4=0, then x=4 ? And y=7?
Sorry, I just get a tad frustrated due to my slightly incompetant teacher who didn't finish teaching us the syllabus :L
4. (Original post by katesimpson2112)
So do you mean that:
If x-4=0, then x=4 ? And y=7?
Sorry, I just get a tad frustrated due to my slightly incompetant teacher who didn't finish teaching us the syllabus :L
Yes.

(Original post by katesimpson2112)
Hi,

Does this mean that y=7 and x=-4 ? Or do I put it into the first equation?
They're both the same equation just written differently so will produce the same result.
5. Thanks, both of you!

Updated: June 4, 2012
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