## Problems on Number Theory and Alzebra (frm BdMO)

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Please don't post problems (by starting a topic) in the "X: Solved" forums. Those forums are only for showcasing the problems for the convenience of the users. You can always post the problems in the main Divisional Math Olympiad forum. Later we shall move that topic with proper formatting, and post in the resource section.
rakeen
Posts: 384
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### Problems on Number Theory and Alzebra (frm BdMO)

1. $2x^2 - 8x + 7$ ei rashi'r sorbocho maan koto?
My Attempt: I firstly turned into this: 2x(x-4)+7 . Then I placed different numbers instead of $x$. Then find that it is -1 . Is it true. Is there any smarter solution?

2. $x$ er $\Re$ maan ber koro jekhane x nicher equation satisfy kore:
$3^x + 4^x = 5^x$

3.$2^4 \times 5^5 \times 10^8$ ei rashite koyti onko ache?
MyAttempt: if we simplyfy $10^8$ to 5 and 2 , then we get : $10^12 \times 5$ And thus the ans is 13! is ti correct?

4. $3^a - 7^b - 1=0$ ei rashir koiti somadhan ase?(very difficult to me)

5.How many subset does this set have $A$ = $\{$ 1,2,3,.....,2003$\}$ .the sum of the elements containing in that subset must be $2007000$.

6. n er koyti purno dhonattok maaner jonno $n^2 - 14n + 24$ 1ti Prime number? (ami sudhu jani prime odd hoy(except 2))

7. n ke 3 diye bhag korle 1 thake, 4diye bhag kore 2 thake, 5 diye bhag korle 3 thake, 6 diye korle 4 thake. 7 diye bhag korle koto bhagsesh thakbe? (pattern dekhe mone hoy 5 hote pare. Kintu 5 diye bhag korle 3 thake. Tai mone hoche 7 diye bhag korle 0 thakbe, kintu prosner sathe milale tao hoy na. )

r@k€€/|/

Moon
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### Re: Problems on Number Theory and Alzebra (frm BdMO)

1. try to make a square and use the idea that the square of a real number is always $\geq 0$.
3. yes, correct!
4. I don't understand your problem 4. Have you written it correctly?
5. $\dfrac{2003\times (2003+1)}{2} = 2 007 006$. Does it help?
6. I guess you should learn some number theory. Read my article on number theory http://www.kmcbd.org/Home/documents (Introduction to Number theory_KMC (By Tarik Adnan Moon).pdf)
"Inspiration is needed in geometry, just as much as in poetry." -- Aleksandr Pushkin

learn how to write equations, and don't forget to read Forum Guide and Rules.

rakeen
Posts: 384
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Location: Dhaka

### Re: Problems on Number Theory and Alzebra (frm BdMO)

5. 0o0o0o0o. Very easy. Just 1. But if we consider proper subset, the result is 0. And would I know that 2003*(2003+1) / 2 = 200700. Jodi bolto sum hobe 200400! tahole?
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rakeen
Posts: 384
Joined: Thu Dec 09, 2010 5:21 pm
Location: Dhaka

### Re: Problems on Number Theory and Alzebra (frm BdMO)

4. was set in BdMO(Div) Comilla 2008 #1.
it says " $a$ and $b$ $\Re$ hole nicher somikoroner koyti somadhan ache? $3^a -7^b -1 = 0$ "
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rakeen
Posts: 384
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Location: Dhaka

### Re: Problems on Number Theory and Alzebra (frm BdMO)

1. ultimately to amake oi 1,2,3..... bosiye dekhte hobe!
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rakeen
Posts: 384
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### Re: Problems on Number Theory and Alzebra (frm BdMO)

hey, prob 2 kothay reply korso?
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Moon
Posts: 751
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### Re: Problems on Number Theory and Alzebra (frm BdMO)

তুমিই তো পোস্ট করছিলা আলাদাভাবে
viewtopic.php?f=8&t=65
এজন্যই তো বলছি:>>>Already replied. But from next time please don't double post.
"Inspiration is needed in geometry, just as much as in poetry." -- Aleksandr Pushkin

learn how to write equations, and don't forget to read Forum Guide and Rules.

AntiviruShahriar
Posts: 125
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### Re: Problems on Number Theory and Alzebra (frm BdMO)

7no::
$3a+1=n=4b+2,theke n{1}=10,22,...........................[10+g12]..{g purnosongkha}$
$n{1}=5c+3$ er jonno 58,118.......{(5x-1)12+10}[n{1} hotee dhara toiri koree]{(5x-1)12+10}x=natural number$eita ki thik ase???????????????? Last edited by AntiviruShahriar on Sat Dec 18, 2010 11:39 am, edited 1 time in total. AntiviruShahriar Posts: 125 Joined: Mon Dec 13, 2010 12:05 pm Location: চট্রগ্রাম,Chittagong Contact: ### Re: Problems on Number Theory and Alzebra (frm BdMO) Moon wrote:1. try to make a square and use the idea that the square of a real number is always$\geq 0$. 2. Already replied. But from next time please don't double post. 3. yes, correct! 4. I don't understand your problem 4. Have you written it correctly? 5.$\dfrac{2003\times (2003+1)}{2} = 2 007 006\$. Does it help?
6. I guess you should learn some number theory. Read my article on number theory http://www.kmcbd.org/Home/documents (Introduction to Number theory_KMC (By Tarik Adnan Moon).pdf)
1 no ta ki সর্বোচ্চ না সর্বনিম্ন হবে????????সর্বোচ্চ হলে তো অসীম হওয়ার কথা।

Dipan
Posts: 158
Joined: Wed Dec 08, 2010 5:36 pm

### Re: Problems on Number Theory and Alzebra (frm BdMO)

Prob 2 er ans to 2.