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Norma-Jean [14]
3 years ago
7

Let FS R be a finite set. (a) Prove that F is closed (b) Prove that every point in F is an isolated point.

Mathematics
1 answer:
Lorico [155]3 years ago
8 0

Answer:

a) Suppose that F is ordered in ascending order: F = \{x_1,\ldots, x_n\}. Then, the complement of F can be written as

F^c = (-\infty,x_1)\cup (x_1,x_2)\cup (x_2,x_3)\cup \cdots \cup (x_{n-1}, x_{n})\cup (x_n,+\infty)

which is the union of a finite number of open intervals, then F^c is an open set. Thus, F is a closed subset of the real numbers.

b) Take an arbitrary element of F, let us say x_k. Now, choose a real number \epsilon such that

0 there are not other element of F, because \epsilon is less that the minimum distance between x_k and its neighbors.

In case that k=1 we only consider 0, and if k=n we only consider 0.

Then, all points of F are isolated.

Step-by-step explanation:

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Answer:

a rise of 20 degrees

Step-by-step explanation:

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The point P(x, y) lies on the terminal side of an angle a = Ū in standard position. What are the signs of the values of x and y?
Akimi4 [234]
I think the answer is both x and y are positive
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Suppose that 5 cards are drawn from a well-shuffled deck of 52 cards. What is the probability that all 5 are not black?
lions [1.4K]
Here's the way I see it:  5 cards are drawn, one by one, without replacement.  Half (or 26) of the original deck are black and half (26) are white.

P(5 are not black) = P(5 are red)

P(5 are not black) = P(first card is red) * P(second card is red) * P(third card is red)*P(fourth card is red)*P(fifth card is red) =

(26/52) * (25/51) * (24/50) * (23/49) * (22/48) = 0.025   (answer)

We start with 52 cards.  We draw one, leaving 51 cards, 25 of which are red.  And so on.
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3 years ago
Use a separate sheet of paper to solve the system of inequalities by graphing. Use the graph to decide if the point (1, –1) is i
Lena [83]

Answer:

The answer is no though, the point (1,-1) is below both.

Step-by-step explanation:

So the two inequalities are y≤-3x+3 and 3x+8y≥3

With inequalities you have to know a few things.  First, when you graph you may have to use non solid lines.  for instance, if you had x<5, 5 would not be part of the answer because it is only answers less than 5.  so you represent this by making a dashed line that says "you cannot include values on this line".  Second, with algebra, if you multiply both sides by a negative it flips the inequality.  for instance -y > 54 you would multiply (or divide) by -1 and it would change to y < -54.  Third, when graphing an inequality, treat it like an equation and graph the line as if it were said equation(with solid or dashed lines as needed)  then, if it is y > f(x) you shade in the section above the line and y < f(x) shades in below.  The shaded part is your answer basically.  Now lets get into yours.

y≤-3x+3

It is already in the form y = f(x)  so grapht he line 3x + 3 with a solid line since it is y is less than or equal to,  then shade below that line.  

3x+8y≥3

First get it so y is by itself

3x+8y≥3

8y≥3 - 3x

y ≥ 3/8 - 3/8 x

Now grapht his line  with a solid line and shade the area above it.

Now, the shaded area below between y ≥ 3/8 - 3/8 x and  y≤-3x+3 and the lines are your answer, so you need to check if the point (1, -1) is in this shared shaded area or on one of the lines.

The answer is no though, the point (1,-1) is below both.

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4 years ago
A. If you know the diameter of a sphere, you can find its radius.
USPshnik [31]

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B. π × r2 × h

7 0
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