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#51 Re: Help Me ! » Curve Sketching » 2006-05-03 00:12:18
So I wont have any questions in the format y = -2x^3 asking in which axis I need to scale?
FYI. The correct term for streching or shrinking the curve is to "scale" it by a "factor" 
#52 Re: Help Me ! » Curve Sketching » 2006-05-02 11:14:51
I know that the curve is exactly the same but if you are asked to describe the transformation, should I say that it's scaled in the y-direction by a factor -2 or in the x-direction by factor -1/2?
#53 Help Me ! » Curve Sketching » 2006-05-02 05:31:13
- RickyOswaldIOW
- Replies: 9
I am having a little trouble with scaling curves, for example:
y = -2x^3
I know that;
y = af(x) is scaled in the y direction by a
y = f(ax) is scaled in the x direction by 1/a
So how can I tell if y = -2x^3 is y = -2f(x) or f(-2x)???
#54 Re: Help Me ! » Quadratic Equations » 2006-04-16 10:55:09
Are they just saying that for the sake of the example that (x + 3)^2 - 2 = 4? That's mighty confusing since the next 50 pages that often use factorising and completing the square assume that f(x) = 0.
#55 Help Me ! » Quadratic Equations » 2006-04-16 10:50:12
- RickyOswaldIOW
- Replies: 4
Happy Easter everyone!
I've just been revising some of my earlier a-level work and I'm a little confused with this:
"Let f(x) = x^2 + 6x + 7.
(a) Put f(x) into completed square form.
(b) Solve the equation f(x) = 4."
I do know how to do all of this but I can't for the life of me see where they are getting f(x) = 4 from?!
#56 Re: Help Me ! » Geometric Progression » 2006-03-29 03:59:45
ux / u(x-1) = ratio
Is this correct?
#57 Re: Help Me ! » Geometric Progression » 2006-03-25 01:25:58
Thanks Ganesh. Will have to study this a bit more 
#58 Re: Help Me ! » How do I do this? » 2006-03-24 17:19:11
I'm 19 and studying a-level mathematics. You're 12 you say? 
#59 Re: Help Me ! » Geometric Progression » 2006-03-24 17:10:33
162 = n² / 18n
Is this along the right track?
#60 Help Me ! » Geometric Progression » 2006-03-24 17:08:10
- RickyOswaldIOW
- Replies: 5
In a GP, u3 = 18 and u5 = 162. Find u1.
I know that in a GP, ux / u(x-1) = ratio (r). I deduce from that;
u5 / n == n / u3.
so 162 / n = n / 18
I then try to balance this - I think that's where I am going wrong.
162 = 2n/18
2916 = 36n
n = 81
Which is of course incorrect. Where am I going wrong?
#61 Re: Help Me ! » Tangent to a Circle » 2006-03-15 09:48:17
edit:
y - 2 = -1(x - 2) --> y = -x + 4.
#62 Re: Help Me ! » Tangent to a Circle » 2006-03-15 09:39:05
Note that it doesn't matter if you take p - c or c - p
Of course
#63 Re: Help Me ! » Largest power of "K" problem...yikes » 2006-03-14 02:48:01
I think you need to replace k with those numbers from a, b, c and d.
3^1 = 3
3^4 = 81
3^13 = 1594323
3^17 = 129140163
Since none of these divide into 40 without a remainder, I'd say the answer is e.
#64 Re: Help Me ! » Tangent to a Circle » 2006-03-14 02:39:51
x² + y² = 8 at (2, 2)
(2)² + (2)² - 8 = 0 (satisfy that the point lies on the circle)
x² + y² = 8
(x + 0)² + (y + 0)² = 8
center point is (0, 0).
0 - 2/0 - 2 = -2 / -2 = 1
the gradient of the radius is 1 and thus the gradient of the tangent is -1.
y - 2 = -1(x - 2) --> y = x + 4.
#65 Help Me ! » Tangent to a Circle » 2006-03-14 02:35:23
- RickyOswaldIOW
- Replies: 4
I need to find the equations of tangents on circles at certain points.
I have the co-ords of the point(p) and the co-ords of the center(c). To work out the gradient of the radius from the center to the point I do:
y(c) - y(p) / x(c) - x(p)
Is this correct or should I take (p) - (c) instead?
#66 Re: Help Me ! » Equation of a Circle. » 2006-03-13 10:49:00
It is indeed edexcel A-level. The book is Core 2 and I study through the National Extensions College.
#67 Re: Help Me ! » Equation of a Circle. » 2006-03-09 05:14:23
im curious as to why ur looking at (y-2)²...?
My question asks "Give the equation of a circle with center (1, 2), radius 3"
and the genral equation for a circle is "(x - a)² + (y - b)² = r²"
hence (y - 2)².
From that question, the book states that the answer is;
(x - 1)² + (y - √2)² = 3
expanded
x² - 2x + y² - 2√2y = 0
very bizarre!
#68 Help Me ! » Equation of a Circle. » 2006-03-08 05:18:40
- RickyOswaldIOW
- Replies: 6
This circle has a center point at (1, 2) and a radius of 3.
According to the genral equation of a circle, that's:
(x - 1)² + (y - 2)² = 3²
expanded:
x² - 2x + 1 + y² - 4y + 4 = 9
and
x² - 2x + y² - 4y = 4?
my book is saying (y - 2) (y - 2) = y² - 2√2y!
(y - 2) (y - 2) = y² - 2y - 2y + 4 in my eyes?!
#69 Re: Help Me ! » one more problem 2 actully 2 » 2006-03-07 23:19:42
Wish them luck from me.
#70 Re: Help Me ! » one more problem 2 actully 2 » 2006-03-07 22:59:16
The smart people seem to be sleeping right now, if you have some time they will be here in a few hours and will solve all your problems
Well, many of your maths related ones at least
#71 Re: Help Me ! » using the quadriatic formula to solve! » 2006-03-07 22:56:20
I think you are right to say
the square root of 1+16
My reasoning is incorrect, it would be pointless to find the square root of a number and then square it again (you end up with the same number)!
#72 Re: Help Me ! » using the quadriatic formula to solve! » 2006-03-07 22:54:38
I hate to say this now but I think I have made a mistake 
#73 Re: Help Me ! » Factor X » 2006-03-07 22:50:27
I did this question 3 times seperately, each time I made the same mistake. (3)^3 = 27 as you state in the first line, I put down 9 each time!!!
#74 Re: Help Me ! » using the quadriatic formula to solve! » 2006-03-07 22:47:04
I think one of your errors is to do
the square root of 1+16
√(1+16) = √17, this is wrong. you should do:
(√1) + 16
#75 Re: Help Me ! » using the quadriatic formula to solve! » 2006-03-07 22:41:54
Also, if you are using a calculator, make sure you are not doing 1 + √1² + (16/4), which would give you an incorrect answer. You can break the sum down:
√1² =
1
+ 16 =
17
+ 1 =
18
/4 =
4.5