Post by: Hielly on March 14, 2009, 09:24:01 am
1.Use a CAS calculator to help answer the following questions.
A pole 11 metres high is firmly secured to the ground. A parabolic arch is to be
attached to the pole 3 metres above the ground as shown in the diagram below. A
metal rod will run directly from the top of the pole straight to the ground so that it just
touches the arch in one position only. Let y be the height above the ground in metres
and x be the distance along the ground from the foot of the pole in metres.
a)The arch is to be modelled by the quadratic equation y = -1/8x^2 + a/4x +3 , where a
is a non-zero positive constant. Find where the arch meets the ground in terms of
a, that is, find the x-intercept.
so we're trying to find A, the x point? not sure what to do
view attachment for picture
Thanks
edit: y=-1/8x^2 + a/4x +3
Post by: Hielly on March 14, 2009, 09:49:26 am
Post by: d0minicz on March 14, 2009, 09:56:07 am
you then use the positive solution
Post by: Hielly on March 14, 2009, 10:01:34 am
Post by: Damo17 on March 14, 2009, 10:14:46 am
i used the quadratic formula using a=-1/8 b=a/4 c=3 and it came out really messy
How did you get them values for a and b?
Post by: Hielly on March 14, 2009, 10:17:17 am
Post by: d0minicz on March 14, 2009, 10:18:44 am
y = – x^2 + x + 3, where a
is a non-zero positive constant.
does that mean theres supposed to be an a in the quadratic equation?
Post by: TrueTears on March 14, 2009, 10:25:50 am
think hielly just edited her post :)y = – x^2 + x + 3, where a
is a non-zero positive constant.
does that mean theres supposed to be an a in the quadratic equation?
Post by: d0minicz on March 14, 2009, 10:30:49 am
Post by: Damo17 on March 14, 2009, 10:33:18 am
Post by: Hielly on March 14, 2009, 10:33:39 am
answer is x=a + square root a^2 +25
Post by: Damo17 on March 14, 2009, 10:45:16 am
Post by: Hielly on March 14, 2009, 10:51:47 am
Post by: Damo17 on March 14, 2009, 11:04:43 am
Sorry for it being messy.
Post by: Hielly on March 14, 2009, 11:11:27 am
sorry i have never encountered so many fractions while doing the quadratic formula
Post by: Damo17 on March 14, 2009, 11:20:00 am
Post by: TrueTears on March 14, 2009, 11:25:50 am
2nd step is incorrect, you can't split up the surd. Although you did get the correct answer the working should be this:
Post by: Damo17 on March 14, 2009, 11:49:56 am
2nd step is incorrect, you can't split up the surd. Although you did get the correct answer the working should be this:
Yeah, always small errors. Thanks
Post by: Hielly on March 14, 2009, 12:45:44 pm
if the equation of the metal rod is modeled by the linear function y=11+bx, find the value of b