Hi all,
Great work on the solution, I'm down to 2(x² - 4x - 8) = 0 but I have never seen the equation -b±√b² - 4ac/2a in my puff I believe, and if I have its been a looonng while since I've used it. Any other way (using more farmiliar higher notes?) that this can be finished off?
Thanks,
Paolo
0
2001 - Paper 1 - Q11(C)
Started by Max018, May 16 2004 09:20 AM
7 replies to this topic
#1
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Posted 16 May 2004 - 09:20 AM
| QUOTE |
| Points of intersection means you can subsitute the y = x + 5 equation into the circle equation: x² + (x + 5)² - 8x - 10(x + 5) + 9 = 0 x² + (x + 5)(x + 5) - 8x - 10x - 50 + 9 = 0 x² + x² + 10x + 25 - 8x - 10x - 41 = 0 2x² - 8x - 16 = 0 2(x² - 4x - 8) = 0 Then using the quadratic formula you can solve for x: -b±√b² - 4ac/2a a = 1 b = -4 c = -8 Substituting these values in should give: 4±√48/2 2 ±(√48/2) 2±(√4√3/2) 2±√2√3 |
#2
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Posted 16 May 2004 - 10:11 PM
You can use the technique of Completing the Square.
2(x² - 4x - 8) = 0
x² - 4x - 8 = 0
x² - 4x = 8
(x-2)² = 8 + 4
x-2 = +/- root12
x = 2 +/- root4*root3
x = 2 +/- 2root3
The final part of what you've quoted above has some errors.
2(x² - 4x - 8) = 0
x² - 4x - 8 = 0
x² - 4x = 8
(x-2)² = 8 + 4
x-2 = +/- root12
x = 2 +/- root4*root3
x = 2 +/- 2root3
The final part of what you've quoted above has some errors.
#3
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Posted 17 May 2004 - 06:49 PM
are you entirely sure you have never seen it before because its SG as far as i know and i think i used it in the exam last year but not entirely sure
If i am not here i am somewhere else
#4
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Posted 18 May 2004 - 09:39 AM
Yes, the quadratic formula is used in Standard Grade - the equation is given in the exam.
#5
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Posted 18 May 2004 - 12:03 PM
| QUOTE (George @ May 18 2004, 09:39 AM) |
| Yes, the quadratic formula is used in Standard Grade - the equation is given in the exam. |
Are you referring to the Standard Grade exam, as it's not given in the Higher exam.
So Max you would probably need to learn it before Friday!
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#6
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Posted 18 May 2004 - 02:59 PM
ach theres always other ways round it 
#7
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Posted 18 May 2004 - 04:21 PM
You use quadratic formula for so many things in AH Maths.
#8
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Posted 18 May 2004 - 10:00 PM
I think it's assumed at Higher and AH that you know the quadratic formula. It's not too hard to learn, given that most of it is the discriminant.
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