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VCE Methods Question Thread!
Dominatorrr:
--- Quote from: b^3 on December 15, 2011, 08:34:38 pm ---
--- Quote from: Dominatorrr on December 15, 2011, 08:30:58 pm ---QUESTION ATTACHED
How do I find the values of a and b?
--- End quote ---
This exact question has been on one of my SACS before. Anyway since the diameter at the top of the structure is 20m, you have the point 20/2=10 away from the origin and up 40m (height) i.e. the point (10,40). Now at the base you have a height of 0 and 50m from the origina so you have the point (50,0). Then plug those two points back into the equation to find a and b.
--- End quote ---
--- Quote from: brightsky on December 15, 2011, 08:36:51 pm ---we know that the graph passes through these points:
(50,0), (-50,0), (10, 40), (-10,40)
so...subbing x and y coordinates:
0 = a/50^2 + b
40 = a/10^2 + b
0 = a + 2500b..[1]
4000= a +100b..[2]
[2]-[1]:
4000 = -2400 b
b = -5/3
so a = 2500*5/3 = 12500/3
hope these correlate to the answers, these numbers look weird.
--- End quote ---
Ah I see, thanks to the both of you and yes, those answers are right.
Dominatorrr:
--- Quote from: Dominatorrr on December 15, 2011, 08:30:58 pm ---QUESTION ATTACHED
How do I find the values of a and b?
--- End quote ---
Another part of this question is "A junior version of the ride is proposed, with the sides of the central structure dilated by a factor of 2 from the y-axis. Find the new equation."
The answer for this question is y=(16666.33/x^2)-1.67. I'm a little confused as to how the 16666.33 was obtained.
dc302:
To dilate by factor of 2 from y-axis means you need to replace x with x/2. This should give you the answer.
Dominatorrr:
--- Quote from: dc302 on December 16, 2011, 11:36:49 am ---To dilate by factor of 2 from y-axis means you need to replace x with x/2. This should give you the answer.
--- End quote ---
Yeah I think it makes sense now.
y=(4167/x^2)-1.67
y=(4167/0.5x*0.5x)-1.67
y=(4167/0.25x^2)-1.67
y=(16668/x^2)-1.67 (CLOSE ENOUGH)
dc302:
--- Quote from: Dominatorrr on December 16, 2011, 05:56:22 pm ---
--- Quote from: dc302 on December 16, 2011, 11:36:49 am ---To dilate by factor of 2 from y-axis means you need to replace x with x/2. This should give you the answer.
--- End quote ---
Yeah I think it makes sense now.
y=(4167/x^2)-1.67
y=(4167/0.5x*0.5x)-1.67
y=(4167/0.25x^2)-1.67
y=(16668/x^2)-1.67 (CLOSE ENOUGH)
--- End quote ---
Yep, and the reason your answer was a little off is because you rounded 12500/3 up to 4167, when it should be 4166.6(recurring)
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