Can anyone help me with part a, I can do 11b, but I have no idea how to do 11a.

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# 2001 paper 2 question 11 a

Started by oddbins, Apr 06 2005 01:26 PM

6 replies to this topic

### #1

Posted 06 April 2005 - 01:26 PM

### #2

Posted 06 April 2005 - 01:45 PM

I struggled with that one too but I got it in the end.

Here's what I done

The equation of a parabola: y= (x-root1)(x-root2)

And you know the roots are: -1, p

So the equation of the Parabola: y= -(x+1)(x-p)

y= -(x -px=x-p)

y= -x +px-x+p

y=p+(px-x)-x

If you need me to explain anything just ask!

Here's what I done

The equation of a parabola: y= (x-root1)(x-root2)

And you know the roots are: -1, p

So the equation of the Parabola: y= -(x+1)(x-p)

y= -(x -px=x-p)

y= -x +px-x+p

y=p+(px-x)-x

__y=p+(p-1)x-x__If you need me to explain anything just ask!

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### #3

Posted 06 April 2005 - 01:56 PM

That helps a lot, thanks. I understand now.

Just one question, why is it y= - (x+1)(x-p) and not just y=(x+1)(x-p), I don't understand why there is a minus in front, or am I just being thick?

Just one question, why is it y= - (x+1)(x-p) and not just y=(x+1)(x-p), I don't understand why there is a minus in front, or am I just being thick?

### #4

Posted 06 April 2005 - 02:00 PM

The sign of x^2 determins whether the parabola is happy or sad shaped... heheh. I can't remember which way it works though, sorryÂ¬

Signatures suck. They clog up websites and serve no purpose.

### #5

Posted 06 April 2005 - 02:02 PM

Lol! No your not think I didn't even know the formula till yesterday!

It has a negative at the start because the graph is negative. The way I'v been taught to remember it is that if the graph looks like a smiley face then it positive if it looks like a sad face then its negative!!!

It has a negative at the start because the graph is negative. The way I'v been taught to remember it is that if the graph looks like a smiley face then it positive if it looks like a sad face then its negative!!!

(`'•.¸(`'•.¸ ¸.•'´)¸.•'´)

**x**..*...**x**.°•.♥.•°.** Amanda loves Craig**.°•.♥.•°.

**x**...*..

**x**

(¸.•'´(¸.•'´ `'•.¸)`'•.¸)

### #6

Posted 06 April 2005 - 02:07 PM

I get it. Because the parabola is sad, it is a minus. And if it was happy it would be positive.

I havn't done parabolas in a while, could you tell?

Thanks for the help! LOL

I havn't done parabolas in a while, could you tell?

Thanks for the help! LOL

### #7

Posted 07 April 2005 - 10:02 AM

QUOTE(oddbins @ Apr 6 2005, 03:07 PM)

I get it. Because the parabola is sad, it is a minus. And if it was happy it would be positive.

I havn't done parabolas in a while, could you tell?Â Â Â

Thanks for the help! LOL

I havn't done parabolas in a while, could you tell?Â Â Â

Thanks for the help! LOL

Yup that's correct. Check out the Polynomials and Quadratics download on page 6.

So, the following parabola is +ve (i.e 'happy):

And the following parabola is -ve (i.e 'sad'):

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