Questions 11(b)- i know roots are x=0 and x=24 (sloloutions say q= -24 how?) how you get p aswell???

Question 12 can get to log e(2e)^3 - log e (3e)^2

cheers

Also there are 2 circle equations how do u know what one to use ? Eg. qu11a ii)

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# Help with Past paper 2003 questions

Started by Stewartd7, May 17 2009 12:57 PM

2 replies to this topic

### #1

Posted 17 May 2009 - 12:57 PM

### #2

Posted 17 May 2009 - 05:42 PM

Q11b q=-24 because, if you look at the equation of the parabola y=px(x+q), the roots occur when y=0 so

0=px(x+q)

x=0, x+q=0, now you knew the second root was x=24

so 24+q=0 so q=-24.

to find p we need another point, ie A (12,-5) which lies on the parabola, subbing that point into the parabola equation

-5=12p(12-24)

-5=-144p

p=5/144

and in general use the equation (x+a)²+(y+b)² =r² for circle questions as it is the easier of the two

Q12

Link to working

so A=1, B=8,C=9

0=px(x+q)

x=0, x+q=0, now you knew the second root was x=24

so 24+q=0 so q=-24.

to find p we need another point, ie A (12,-5) which lies on the parabola, subbing that point into the parabola equation

-5=12p(12-24)

-5=-144p

p=5/144

and in general use the equation (x+a)²+(y+b)² =r² for circle questions as it is the easier of the two

Q12

Link to working

so A=1, B=8,C=9

**=-=-=Marcus=-=-=**### #3

Posted 17 May 2009 - 07:47 PM

QUOTE (Marcus @ May 17 2009, 06:42 PM) <{POST_SNAPBACK}>

Q11b q=-24 because, if you look at the equation of the parabola y=px(x+q), the roots occur when y=0 so

0=px(x+q)

x=0, x+q=0, now you knew the second root was x=24

so 24+q=0 so q=-24.

to find p we need another point, ie A (12,-5) which lies on the parabola, subbing that point into the parabola equation

-5=12p(12-24)

-5=-144p

p=5/144

and in general use the equation (x+a)²+(y+b)² =r² for circle questions as it is the easier of the two

Q12

Link to working

so A=1, B=8,C=9

0=px(x+q)

x=0, x+q=0, now you knew the second root was x=24

so 24+q=0 so q=-24.

to find p we need another point, ie A (12,-5) which lies on the parabola, subbing that point into the parabola equation

-5=12p(12-24)

-5=-144p

p=5/144

and in general use the equation (x+a)²+(y+b)² =r² for circle questions as it is the easier of the two

Q12

Link to working

so A=1, B=8,C=9

gr8 thanks alot for ur help m8

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