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Show that if f(n) is O(g(n)) and d(n) is O(h(n)) then f(n) + d(n) is O(g(n) + h(n)).

GaryK [48]

$f(n)\in\mathcal O(g(n))$ is to say

$|f(n)|\le M_1|g(n)|$

for all $n$ beyond some fixed $n_1$ .

Similarly, $d(n)\in\mathcal O(h(n))$ is to say

$|d(n)|\le M_2|h(n)|$

for all $n\ge n_2$ .

From this we can gather that

$|f(n)+d(n)|\le|f(n)|+|d(n)|\le M_1|g(n)|+M_2|h(n)|\le M(|g(n)|+|h(n)|)$

where $M$ is the larger of the two values $M_1$ and $M_2$ , or $M=\max\{M_1,M_2\}$ . Then the last term is bounded above by

$M(|g(n)|+|h(n)|)\le2M\max\{|g(n)|,|h(n)|\}$

from which it follows that

$f(n)+d(n)\in\mathcal O(\max\{g(n),h(n)\})$

3 0

2 years ago

Determine the domain of the function (f o g)(x) where f(x)= 3/x+2 and g=5/x.

vitfil [10]

Answer:

The Domain is all real values of x except x = 0 and x = -2.5.

Step-by-step explanation:

I am assuming that f(x) = 3/(x + 2).

(f o g)x is found by substituting 5/x for the x in 3/(x + 2).

(f o g) x = 3/ ( 5/x + 2)

= 3 / ( 5+2x) / x

= 3x / (5 + 2x).

When finding the domain you first check for values of x which make g(x) undefined then values of x which make (f o g)(x) undefined.

x = 0 makes g(x) = 5/0 so it is undefined and x = -2.5 makes g o f undefined also.

7 0

3 years ago

A random sample of 85 sixth-graders in a large city take a course designed to improve scores on a reading comprehension test. Ba

BartSMP [9]

Answer:

$12.6 < \mu < 14.8$

For this case we can find the margin of error like this:

$ME= \frac{14.8-12.6}{2}= 1.1$

Since we need to divide the width of the interval by 2.

And now with the margin of error we can find the sample mean with any of the two following ways:

$12.6 +1.1=13.7$

$14.8-1.1=13.7$

So for this case the correct answer would be:

A. Sample Mean = 13.7; Margin of Error = 1.1

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

Solution to the problem

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)