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#1 Help Me ! » who have the prove of tanh(x+y)? » 2018-02-18 12:19:02

Hannibal lecter
Replies: 1

Hi,

prove :-

tanh(x + y) = (tanh x + tanh y)/(1 + tanh x + tanh y)

#3 Help Me ! » question about interval and the graph of function (inc and dec).. » 2018-02-13 22:27:22

Hannibal lecter
Replies: 3

Hi, I'll provide to images from the textbook , one is the question and the second image is the answers
but I need the explanation of answer b)
because I sub 2008 from 25 = 1983 hence it most be the 7.019
and when I sub 2008 from 50 = 1958 have it most be 6.992

I see a different answers , can you tell me what is the true answers?

2018_02_14_132229.png



2018_02_14_132215.png


as you see the is a contradictory and contradictory answers

any help please? why he math the year 1958 to 7.019
and the year 1983 to 6.992???

isn't that wrong?

#4 Re: Help Me ! » the largest interval on the following table » 2018-02-13 21:26:46

and this is a picture of the full question :-

2018_02_14_122550.png



a) answer : is 2008-2009

b) answer is :  2005-2007

can you explain to me again in other way please

#5 Re: Help Me ! » the largest interval on the following table » 2018-02-13 21:14:57

or the reason is just just because there is  a negative sing in the middle of the graph

#6 Re: Help Me ! » the largest interval on the following table » 2018-02-07 07:20:10

zetafunc wrote:
Hannibal lecter wrote:

and the second question is : Q2)  Find the largest time interval over which the actual US consumption of biodiesel was an increasing function of time. Interpret what increasing means, practically speaking, in this case.

I found the answer is for Q2 :-

The largest time interval was 2005–2007 since the percentage growth rates were positive for each of these three consecutive years. This means that the amount of biofuels consumed in the US steadily increased during the three year span from 2005 to 2007, then decreased in 2008


that don't make any sense? the first answer of Q1 say the largest interval is from 2008-2009
and the second answer for the Q2 said that the largest interval from 2005-2007? as well as it'a a decreasing function not increasing! ( over this interleave )

Because the table refers to percentage growth. If it grew by a positive percentage in 2005, 2006 and 2007, then the biodiesel consumption was still increasing in those years, but it was just growing more slowly in 2007 compared to 2006 and 2005.

The biodiesel consumption decreased in 2008, because its percentage is negative. Then it grew a little bit in 2009, because the percentage is positive.

so you mean it's like +%236 and +%186.6 and so on?

so it's increasing always???

#7 Re: Help Me ! » the largest interval on the following table » 2018-02-07 07:16:50

zetafunc wrote:
Hannibal lecter wrote:

Hi,

The table shows the recent annual percent growth in US biodiesel consumption

https://preview.ibb.co/kDyByx/2018_02_04_151626.png

find largest time interval over which the percentage growth in the US consumption of biodiesel was an increasing function of time


I found the answer is :  largest interval was 2008–2009 since the percentage growth rate increased from−11.7 to 7.3
(Note that the percentage growth rate was a decreasing function of time over 2005–2007.)



but why it's not from 2005 - 2006?
which gives  237 to 186.6 , isn't that the largest interval

The key word here is that we want to find the largest time interval where the percentage growth was an increasing function of time. Imagine plotting a graph with years on the x-axis and percentage growth on the y-axis -- what would it look like?


The largest time interval was 2005–2007 since the percentage growth rates were positive for each of these three consecutive years. This means that the amount of biofuels consumed in the US steadily increased during the three year span from 2005 to 2007, then decreased in 2008
_____________________+++++

first how it is " steadily increased during the three year" ? it's 237  to  186.6 then 37.2, how  it's increased? I see deacreainsg
second : what is the meaning of  "the actual US consumption"

because there is a two question as you saw a) and b) , the a) says  Find the largest time interval over which the percentage growth in the US consumption of biodiesel was an increasing function of time.......

and the b) says : Find the largest time interval over which the actual US consumption of biodiesel was an increasing function of time.....

can you explain these to me please

#8 Re: Help Me ! » the largest interval on the following table » 2018-02-04 00:29:19

and the second question is : Q2)  Find the largest time interval over which the actual US consumption of biodiesel was an increasing function of time. Interpret what increasing means, practically speaking, in this case.

I found the answer is for Q2 :-

The largest time interval was 2005–2007 since the percentage growth rates were positive for each of these three consecutive years. This means that the amount of biofuels consumed in the US steadily increased during the three year span from 2005 to 2007, then decreased in 2008


that don't make any sense? the first answer of Q1 say the largest interval is from 2008-2009
and the second answer for the Q2 said that the largest interval from 2005-2007? as well as it'a a decreasing function not increasing! ( over this interleave )

#9 Re: Help Me ! » can two lines be perpendicular and parallel at the same time? » 2018-02-04 00:22:43

sorry but the orignal line was y = -4x + 7   the slop not positive I'm talking about this case

but thanks anyway I solved  all the question about that field

#10 Help Me ! » the largest interval on the following table » 2018-02-04 00:20:08

Hannibal lecter
Replies: 7

Hi,

The table shows the recent annual percent growth in US biodiesel consumption

2018_02_04_151626.png

find largest time interval over which the percentage growth in the US consumption of biodiesel was an increasing function of time


I found the answer is :  largest interval was 2008–2009 since the percentage growth rate increased from−11.7 to 7.3
(Note that the percentage growth rate was a decreasing function of time over 2005–2007.)



but why it's not from 2005 - 2006?
which gives  237 to 186.6 , isn't that the largest interval

#11 Re: Help Me ! » can two lines be perpendicular and parallel at the same time? » 2018-02-03 22:58:05

I think It's -1/-4  which gives 1/4 positive not negative I think my answer was not correct

so the line is y=0.25x + 4.75

#16 Re: Help Me ! » important question about Volum of sphare » 2018-02-03 02:27:30

The average velocity, v, for a trip over a fixed distance, d, is inversely proportional to the time of travel, t.

which is v= d/t

there is no a constant of proportionality here why?

with compare to other questions like that ( The number of animal species, N, of a certain body length, l, is inversely proportional to the square of l. )
which it N =k/l^2

now there is a constant again!

I got confused, when we put that " k " and when not?

#17 Help Me ! » important question about Volum of sphare » 2018-02-03 02:18:39

Hannibal lecter
Replies: 2

Hi,

write formula representing the function which it the volume of a sphere is proportional to the cube of its radius, r. ?

I found the answer if V= kr^3 which is V = 3/4*pi*r^3

how is that be??

before I look to the answer I solve it in my papers and wrote ( V= r^3 )

but I didn't wrote the 3/4*pi*!!
from where the solver bring this values ...

#18 Help Me ! » can two lines be perpendicular and parallel at the same time? » 2018-02-03 01:56:17

Hannibal lecter
Replies: 11

Hi,

can two lines be perpendicular and parallel at the same time?

if not...then what is mean the following ? :-

Find equations for the lines through the point (1,5) that are parallel to and perpendicular to the lines the equation y + 4x =7


if the answer is not how can that be " that are parallel to and perpendicular to .. " ???

#21 Re: Help Me ! » a montonic funtion » 2018-02-03 00:30:34

is there a full example of the strictly increasing that you mention with number 7 and 3 please? and with a graph please


abut the monotonically increasing, if it's the same why we put ≤  ? what is that mean

#22 Help Me ! » determine slope of an equation without using dervitice » 2018-02-03 00:26:32

Hannibal lecter
Replies: 3

Hi,

how to calculate the slop of the following equation :

2y +5x−8=0

without using the derivative

I really forget the way

#23 Re: Help Me ! » a montonic funtion » 2018-02-03 00:12:12

yes that's help me too much I understand now what is the meaning of all of this

but I want to know more about the conditions ?

when x1 < x2 then f(x1) ≥ f(x2)         Decreasing
when x1 < x2 then f(x1) > f(x2)         Strictly Decreasing


and the rest of the other condition of monotonic and increasing
why I can't understand this conditions while I have an understanding of increasing/decreasing function ?

can you provide to me an explanation for these conditions please and how to solve a specific exercise

#24 Re: Help Me ! » a montonic funtion » 2018-02-02 09:01:37

thanks,

but about the Strictly increasing/decreasing
I didn't understand, can you provide for me an examples?

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