Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
read more ..

Melody Apr 2, 2022

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Reporting problems.

There are a number of people having problems at the moment.
If you lodge an error can you please give all relevant information that you can think of.
Where you are in the world - the city or the country - is often very important information. read more ..

Melody Mar 16, 2022

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How to make an empty rectangle in Latex

I just worked out how to make an empty box of various horizonal size easily in LaTex.
This is not a recommended method, but other methods that I have tried here have not worked.
This coding is really simple. Just put letters inside read more ..

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Melody Mar 15, 2022

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HAPPY ANNIVERSARY CHRIS! (CPhill)

I just realized that you became a member here exactly 8 years ago today!

It has been great to have you here all that time

off-topic

Melody Mar 13, 2022

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WELCOME BACK CPHILL !

Melody Feb 11, 2022

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Very interesting question. No high level maths required.

This question was posted a couple of days ago.
https://web2.0calc.com/questions/geometry_73561

I think it is really interesting. It looks much more difficult than it really needs to be. read more ..

Melody Feb 1, 2022

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Members have a better experience. Their questions get more attention.

Almost everyone is posting as a guest.
If you post as a member your questions will have a far greater chance of a timely and helpful response.
If you are a genuine learner and interact with us, you will become known and answerers will do read more ..

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Melody Jan 9, 2022

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HAPPY BIRTHDAY CHRIS!

Melody Dec 20, 2021

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Some guidelines for question askers.

Please note:
1) Ask only one question per post.
2) When asking a question talk about what you have tried for yourself. Then people will take you more seriously and will be more able and willing to help.
3) If you get an answer read more ..

off-topic

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Melody Nov 4, 2021

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Remeniscing - a little historical humour.

I just found this old post that some of you, who have been around for a while, might find amusing.

https://web2.0calc.com/questions/look-at-the-new-leader-board

off-topic

Melody Oct 29, 2021

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That is ok, you will remember it now. Glad I could help.

MelodyOct 13, 2013

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I am sorry, you were right but so was your book.

1/root2 = (1*root2)/(root2*root2) = root2/2

The author has rationalized the denominator (made the fraction so that the bottom is rational)

It is considered to be simplified if the demoninator is rational.

MelodyOct 13, 2013

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3x+8=5x-20=5x+4y

Use 3x+8=5x-20 to get the value of x
substitute in x to get the value of y.

I hope this will be enough help.

MelodyOct 13, 2013

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2*10^3+1.9*10^2

dndlocke is correct but the answer he/she got is not finished because it is not in scientific notation.
21.9*10 ²

= 2.19*10*10 ²

= 2.19*10 ³

You also could have done it on your calculator
2 exp 3 + 1.9 exp 2 =
The answer is 2190
But then you have to change it to scientific notation by yourself, I've never owned a calculator that will do that for you.
the exp button on your calc may look like 10 ^x

MelodyOct 13, 2013

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the answer in the book is wrong.
You are correct.

MelodyOct 13, 2013

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Mujib has factorised correctly. Mujib and I both assumed that you were asked to factorise, maybe you were asked to graph? Thinking about it that is probably moe likely but you have to start the same way anyway.

Your problem was

y=x ²+2x-15
so
y= ²+2x-15

To factorise you need to look for 2 numbers
that multiply together to give -15
and add together to give 2
(3 and 5 might be worth looking at)

Since they multiply to give a negative number, one is pos and the other neg
Since they add to a positive, the bigger number is the positive one.
so, 5 and -3 work
hence
y=(x+3)(x-2)

MelodyOct 13, 2013

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If you just wanted
sin(a negative angle) Mujib is right.

sin(-theta) = -sin(theta)

I don't think that this is what you were asking.

MelodyOct 13, 2013

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Just in case you have already seen my answer, I did fix a little typo in the first line of the solution.

MelodyOct 13, 2013

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Okay, I still don't understand, maybe you are studying maths that I have not done or maybe the meaning just gets lost in the translation.
I have not heard the term potencial equation before, do you just mean an equation that is not exponential? (no powers)

Your original question was
how trasform I(z)=I(0)*e^ln(1/10)*z in a potencial equation?
I am going to assume l is a function.

I(z)=I(0) * e ^ln(1/10) * z

I(z)=I(0) * (1/10) * z

I(z)=I(0) * z * (1/10)

I(z)=I(0) * z / 10
-------------------------------

l(0) = l(0) * 0/10 = 0
so
I(z)=I(0) * z / 10 = 0*z/10 = 0

So, with my limited understanding of your problem I get an answer of 0

MelodyOct 13, 2013

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I am sorry I don't understand your question.

how trasform I(z)=I(0)*e^ln(1/10)*z in a potencial equation??

x(z)?
I(0)?

e ^ln(1/10) = 1/10
e and log _e cancel each other out but that is all I can help with. I don't understand the rest of your question.

MelodyOct 12, 2013