Melody

It is good that you had a go guest but  I do not think your method can work.

For instance, the second person may not be different from the first,  

No apology necessary.  Thank you for your kind words :)

Thanks Alan and guest.

I always need reminding about matrices :)

I think EP has given you the intended asnwer

BUT

The question doesn't really make sense.

Why mention noon?

I think it means that the angle of alevation of the sun is 30 degrees.  (the tree is just a tool for this)

If you knew what the date was you could work out the latitude of the tree with this infomration.  

I wonder if this question was written by somoeone who does not have English as a first language.

Or maybe it has been run through a translator at some point in time .....

Thanks guest and asinus, it is a fascinating cake and a great message but it is not my birthday  ......

Maybe I can have 2 birthdays this year      Cool!   

12*nCr(18,7)*(1/12)^7*(11/12)^11 = 0.0040925417608967

That is the probability of getting 7 in the same month but it includes the probability of getting 7 in 2 different months as well.  I mean it includes it twice.

So you would have to subtract

18C7 * (1/12)^7 * (11/12)^11    *    11C7 * (1/12)^7 * (11/12)^4 *  12C2 

nCr(18,7)*(1/12)^7*(11/12)^11*nCr(11,7)*(1/12)^7*(11/12)^4*nCr(12,2)=0.0000001463682172

I'm reasonably confident on the first part but have less confidence on the secontd part (the part to be subrtracted)

0.0040925417608967-0.0000001463682172 = 0.0040923953926795

Do you understand what EP is telling you ?

Yes, yu wre right the first time.  c=0

so now you have    

\(f(x)=ax^2+bx\\ now \;what? \)

sub in the other 2 and you will get two equations that you can solve simultaneously to get a and b.

Give it a go and get back to us with what you have tried  

Thanks EP

Hi Guest, it is really good that you are interacting with EP

Why don't you get an account and get known to us.  

In general, you will get a get a much better deal that way and it is really nice for us, (existing members) to have polite and keen students as a part of our community here.  

f(0)=0  what can you get from that?

Thanks Alan