Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 Re: Introductions » Hi there. » 2018-07-03 03:03:20

Hi Stuti55,

Welcome to the forum.

#2 Re: Help Me ! » Division » 2018-07-02 20:30:53

Hi Zeeshan,

I've moved your thread to the Help Me ! forum.

Have you checked out Maths Is Fun's page on long division?

#3 Re: Help Me ! » Precalculus Help » 2018-06-19 09:28:17

Hi Anduin,

Welcome to the forum. What features does the graph y = sin(x) have? How do they compare to the graphs y = 2sin(x) and y = 3sin(x)?

#4 Re: Help Me ! » algebra » 2018-05-27 22:57:19

Hello,

I noticed that you've posted several times here as a guest. Why not register an account with us?

What have you tried? What sorts of restrictions do you think you can place on x and y?

#5 Re: Help Me ! » Algebra » 2018-05-07 08:27:45

Grantingriver wrote:

Hi Zetafunc, if there are duplicate roots of a polymolial you should counts them as distinct roots.

Why? Precisely the opposite is true: if a root is repeated, then we cannot call those repeated roots 'distinct', and whether or not we count them in the same way we would distinct roots depends on the context.

Grantingriver wrote:

For example, if you say that a give polynomial has “exactly” the roots -3, 4 and 8 that means there is no duplicate roots.

I am not convinced that the word 'exactly' necessarily implies distinctness -- I would have thought that the multiplicities were worth consideration, otherwise the problem appears to be a little simplistic.

#6 Re: Help Me ! » Algebra » 2018-05-05 20:41:44

Grantingriver wrote:

The answer for part 1 is, by all means, yes. This is so because the condition that f(x) has the zeros -3,4 and 8 entails that:
f(x)=(x+3)×(x-4)×(x-8)
And since the zeros of g(x) are -5,-3, 2, 4 and 8 we also have:
g(x)=(x+5)×(x+3)×(x-2)×(x-4)×(x-8)
and hence:
g(x)/f(x)=[(x+5)×(x+3)×(x-2)×(x-4)×(x-8)]/[(x+3)×(x-4)×(x-8)]=(x+5)×(x-2)
and since the result of the division (x+5)×(x-2) is a polynomial without a remainer, therefore g(x) is divisible by f(x).  The answer of part 2 is very clear from the answer of part 1. For a polynomial g(x) to be divisible by a polynomial f(x) at least all the roots (zeros) of f(x) should be also roots (zeros) of g(x). And the final statement completes the answer.

This is not quite true: the multiplicities of the zeroes are important, e.g.
  and 
.

#7 Re: Help Me ! » Help Me ! » 2018-04-30 06:42:02

Hello bishop.bell,

Welcome to the forum. This problem has been asked at least twice in the past -- you can find some discussions about it here and here.

#8 Re: Help Me ! » a question of a dice in probabilty » 2018-03-30 21:10:17

The denominator will not be 36. Remember: you want to restrict the number of possible outcomes to include only those that have a '5' in them.

#9 Re: Help Me ! » [ASK] Integral » 2018-03-18 05:42:18

The question as it stands has no answer (the area would be infinite). There is probably a typo in the question.

#10 Re: Help Me ! » [ASK] Integral » 2018-03-18 04:54:32

The integral should evaluate to
. Your arithmetic slips take place in these three lines:



In particular, the second pair of brackets in the second line and the first pair of brackets in the third line are not correct.

However, the question appears to be badly worded. The area 'bounded' by the curve, the axes and the line x = 2 is not bounded at all -- it is infinite.

#12 Re: Help Me ! » [ASK] Professional Goalkeeper » 2018-03-17 21:41:25

Yes -- do you know how to calculate this?

#13 Re: Help Me ! » [ASK] Professional Goalkeeper » 2018-03-17 19:34:15

One way is to use the binomial distribution.

Suppose that
represents the number of times that the goalkeeper saves a penalty. Then,
has a binomial distribution:

You want to calculate
. Do you see why?

#14 Re: Help Me ! » Probability Statistics: Please help! » 2018-03-14 00:18:34

Hi MellyBigD,

Welcome to the forum. You have posted 4 threads asking for help, but you have not shown any attempts at the problems or given any pointers about where you are stuck. We will endeavour to help you as best you can, and we happily volunteer our time to do so, but we will not do your homework for you. Can you please show some attempts at these problems, or be specific about what exactly you are stuck on?

#16 Re: Help Me ! » how can the sample space of rolling a two dice 36 ? isn't it 42? » 2018-03-08 09:57:17

Getting a 5 on the first die and a 5 on the second die is the same as getting a 5 on the second die and a 5 on the first die.

#17 Re: Help Me ! » math » 2018-02-13 17:40:05

What happens when x is greater than or equal to 1?

#18 Re: Help Me ! » Math » 2018-02-13 17:35:43

What is the limit of your function as x approaches 2?

#19 Re: This is Cool » the Mythical formula to calculate Numerical Derivatives! » 2018-02-12 08:14:24

These coefficients are part of a more general phenomenon called the Savitzky-Golay filter in numerical analysis. In fact the traditional five-point 'stencil' reads:

where
. You can derive this result simply by playing around with the Taylor series for
with
. It's a little tedious, but you can see the derivation here: https://en.wikipedia.org/wiki/Five-poin … he_formula

There are analogous formulae for higher order derivatives too, and several published papers about the error term.

#20 Re: Help Me ! » Calculus 1 » 2018-02-11 19:27:27

Hi Sara,

Thanks for stopping by -- have you considered registering an account with us?

Have you heard of the chain rule, i.e.
?

#21 Re: Help Me ! » Please Check My Work Regarding Limit » 2018-02-07 20:01:15

Monox D. I-Fly wrote:

So, the approximation of x doesn't have to be 0 to make it equals 1?

#22 Re: Introductions » where is bobbym? » 2018-02-04 01:09:19

Bobbym sadly left us last year. We all miss him very much. There is a thread dedicated to him here: http://www.mathisfunforum.com/viewtopic.php?id=23912

#23 Re: Help Me ! » the largest interval on the following table » 2018-02-04 01:07:40

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.

#24 Re: Help Me ! » the largest interval on the following table » 2018-02-04 01:04:19

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?

#25 Re: Help Me ! » can two lines be perpendicular and parallel at the same time? » 2018-02-04 00:56:51

Ah, I see -- my apologies, I misread the original equation. In that case, you are completely correct.

Board footer

Powered by FluxBB