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#1 Re: Help Me ! » Geometric Series » 2016-08-18 09:29:07

The answer to 8 is 500...

9. Suppose 0< a,b,c < 1 and ab + bc + ca = 1. Find the minimum value of a + b + c + abc.

I've tried using AM-GM on this and I can get an inequality for ab+bc+ca and a+b+c in respect to abc but I'm not sure how to answer the problem...

#2 Re: Help Me ! » Geometric Series » 2016-08-17 02:17:42

7. Let

and
denote those areas within the ellipse
that are in the first, second, third, and fourth quadrants, respectively. Determine the value of
.

8. An ellipse and a hyperbola have the same foci, A and B, and intersect at four points. The ellipse has major axis 50, and minor axis 40. The hyperbola has conjugate axis of length 20. Let P be a point on both the hyperbola and ellipse. What is PA * PB?

#3 Re: Help Me ! » Geometric Series » 2016-08-17 00:21:55

@bobby: For number 4 I went back and I found that if you set the entire thing equal to some number n and put in exponent form you can solve for both x and y^5z with some manipulation. It can be done using trial and error, but there is a cleaner way.

@thickhead and ElainaVW:
I understand how to do number 5 now - I personally think it's more important to understand how to do it than to know the exact answer when you're learning, but in applied mathematics a small mistake can be fatal.

#4 Re: Help Me ! » Geometric Series » 2016-08-16 15:42:05

Yes, they were all correct. I understand how to get 3 and 5 now, but I still don't get 4. Thanks for all your help!

#5 Re: Help Me ! » Geometric Series » 2016-08-16 12:09:21

6. Find all ordered pairs of real numbers

such that
.

How did you get the answer to the above?

#6 Re: Help Me ! » Geometric Series » 2016-08-16 07:54:55

Let $$N = \sum_{k = 1}^{1000}k(\lceil \log_{\sqrt {2}}k\rceil - \lfloor \log_{\sqrt {2}}k \rfloor). $$
Find $N$.

How do I use LaTeX?

#7 Re: Help Me ! » Geometric Series » 2016-08-15 23:49:54

bobbym wrote:

Hi aleph_zero;

There is a unique ordered pair (c,d) such that c*phi^n + d^*phi hat ^ n$ is the closed form for sequence A_n.

What does ^* mean?

Sorry, that should just be a * (multiplication)

@thickhead
I can't find x though...

#8 Re: Help Me ! » Geometric Series » 2016-08-15 04:55:02

@bobby
I made a mistake simplifying one of the fractions in Problem 2...Thanks.

3.
Let
A_0 = 6
A_1 = 5
A_n = A_{n - 1} + A_{n - 2} for n ≥ 2
There is a unique ordered pair (c,d) such that c*phi^n + d^*phi hat ^ n$ is the closed form for sequence A_n.
Find c.
Note: phi is the golden ratio, phi hat is the complex conjugate

4. Let x, y, and z be positive real numbers that satisfy
2 log_x (2y) = 2 log_{2x} (4z) = log_{2x^4} (8yz) ≠ 0.
The value of xy^5z can be expressed in the form 1/(2^(p/q)), where p and q are relatively prime positive integers. Find p + q.

#9 Re: Help Me ! » Geometric Series » 2016-08-12 03:32:08

A sequence of real numbers (x_n) is defined recursively as follows: x_0=a and x_1=b are positive real numbers, and
x_(n+2) = (x_(n+1)+1)/(x_n)
for n = 0, 1, 2,.... Find the value of x_{2012}, in terms of a and b.

I've tried finding a pattern, but the calculations get messy pretty quickly. Help?

#10 Help Me ! » Geometric Series » 2016-08-11 09:24:28

aleph_zero
Replies: 66

If a/b rounded to the nearest trillionth is 0.008012018027, where a and b are positive integers, what is the smallest possible value of a+b?

How do I do this problem? Thanks.

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