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 #1
avatar+118613 
+3

Find the derivative of the function by using the definition of the derivative.

f(x)=(x+1)/(x-1)

 

REMEMBER: The first derivative  IS  the gradient of the tangent to the curve

 

Basically when you find this from first principals you take the gradient of the secant.

I want the gradient of the tangent at (x,f(x))

So I have found the gradient of the SECANT  from  (x,f(x)) to the point   (x+c, f(x+c))

THEN I find the limit of this as c tends to 0

This limit will be  the gradient of the TANGENT at (x,f(x)).

 

 

In my case this is

    (That is not written technically at all)

 

This can be expressed in a couple of different ways.  This is one of them.

 

\(f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{f(x+c)-f(x)}{(x+c)-x}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{\frac{x+c+1}{x+c-1}-\frac{x+1}{x-1}}{c}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{\frac{(x+c+1)(x-1)}{(x+c-1)(x-1)}-\frac{(x+1)(x+c-1)}{(x-1)(x+c-1)}}{c}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{\frac{(x+c+1)(x-1)-(x+1)(x+c-1)}{(x+c-1)(x-1)}}{c}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{\frac{x(x+c+1)-1(x+c+1) -x(x+c-1)-1(x+c-1)}{(x+c-1)(x-1)}}{c}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{\frac{2x-2(x+c) }{(x+c-1)(x-1)}}{c}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{-2c}{(x+c-1)(x-1)}\times \frac{1}{c}\\ f'(x)=\displaystyle \lim _{c\rightarrow 0} \frac{-2}{(x+c-1)(x-1)}\\ f'(x)=\frac{-2}{(x-1)^2} \)

 

 

Check using quotient rule.

 

f(x)=(x+1)/(x-1)

\(f(x)=\frac{(x+1)}{(x-1)}\\ f'(x)=\frac{(x-1)*1-(x+1)*1}{(x-1)^2}\\ f'(x)=\frac{-2}{(x-1)^2}\\\)

Great :)

Apr 3, 2019
 #3
avatar+15 
0

so on the last post i couldn't reply cause it was locked, but i already answered them on my own. i don't know how to delete the questions sorry about that, and i wasn't really expecting to gett an answer but courage the cowardly dog helped so i was able to solve the other one's by myself

but for any other person having a hard time answering the questions these were my answers


1. A normal distribution has a mean of 103 and a standard deviation of 2.7.
What is the z-score of 105?

Answer: 0.74

 

2. A normal distribution has a mean of 103 and a standard deviation of 2.7.

What is the z-score of 105?

Answer: 17.8

3. Use technology or a z-score table to answer the question.

The weights of logs in a wood pile are normally distributed with a mean of 17 pounds and a standard deviation of 3.4 pounds. The wood pile is composed of 325 logs.

How many of the logs will weigh 15 pounds or more

Answer: 235

4. The ages of members of a policy action group are normally distributed with a mean of 33 years and a standard deviation of 2 years.
There are 400 members in the group.
About how many members are expected to be between 29 years old and 37 years old

Answer: 380

5. Use technology or a z-score table to answer the question.

The expression  P(z<1.71) represents the area under the standard normal curve below the given value of z.

What is  P(z<1.71)?

Answer: 0.9564

6.  Use technology or a z-distribution table to find the indicated area.

The weights of tomatoes in a bin are normally distributed with a mean of 120 grams and a standard deviation of 4.3 grams.

Approximately 40% of the tomatoes weigh less than which amount?

Answer: 119 g

7. Suppose the scores on a grammar quiz are normally distributed with a mean of 76 and a standard deviation of 8.

Which group describes 16% of the population of grammar quiz scores?

Answer: scores below 68

8.

Select Yes or No to state whether each data set is likely to be normally distributed.

 

Data Set

the weights of the babies born at a hospital yes/no

the number of babies born each month at a hospital yes/no

the number of rooms on each floor of a hospital yes/no

the lengths of the babies born at a hospital yes/no

                        

Answer: yes, yes, no, yes

9. The masses of the oranges on sale at a farm stand are normally distributed with a mean of 239 grams and a standard deviation of 25 grams

Answer 0.8

10. The heights of the peach trees in an orchard are normally distributed with a mean of 12.5 feet and a standard deviation of 1.8 feet.

What is the height of a peach tree with a z-score of −0.5−0.5 ?

Answer: 11.6

11. Use technology or a z-distribution table to find the indicated area.

The masses of the eggs collected on a farm are normally distributed with a mean of 55 grams and a standard deviation of 4.2 grams.

Approximately 80% of the eggs on the farm have a mass greater than which mass?

Answer: 51.5 g

12. Use technology or a z-score table to answer the question.

The weights of boxes of rice produced at a factory are normally distributed with a mean of 24 ounces and a standard deviation of 1.3 ounces. Consider a shipment of 1200 boxes of rice.

How many of the boxes will weigh 25 ounces or less?

Answer: 935

 

btw wont post the other 50 questions on the study guide , any onlookers just look at pavlov's formula and the way he/she answered it

Apr 3, 2019
Apr 2, 2019
 #3
avatar+219 
-3
Apr 2, 2019
 #2
avatar+1011 
-4
Apr 2, 2019

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