2015 regional Secondary no. 6 function algebra

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Md. Rifat uddin
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2015 regional Secondary no. 6 function algebra

Unread post by Md. Rifat uddin » Sat Jan 07, 2017 10:16 pm

Plz solve this problem...... Thanks in advance.....
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asif e elahi
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Location: Sylhet,Bangladesh

Re: 2015 regional Secondary no. 6 function algebra

Unread post by asif e elahi » Sun Jan 08, 2017 2:30 pm

Hint
\begin{align*}
2015=&4\times 503+3\\
503=&4\times 125+3\\
125=&5^3
\end{align*}

mdhasib
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Re: 2015 regional Secondary no. 6 function algebra

Unread post by mdhasib » Mon Jan 09, 2017 12:04 pm

Suppose F(x)=ax+b , then F(F(x))=(a^2)x+ab+b if we compare 4x+3 with (a^2)x+ab+b then we will get F(x)=2x+1 or F(x)=-2x-3 Considering the next statement we can be sure that F(x)=2x+1 .Hence F(2015)=(2*2015)+1=4031 :D :D :D :D

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asif e elahi
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Re: 2015 regional Secondary no. 6 function algebra

Unread post by asif e elahi » Mon Jan 09, 2017 2:23 pm

mdhasib wrote:Suppose F(x)=ax+b , then F(F(x))=(a^2)x+ab+b if we compare 4x+3 with (a^2)x+ab+b
$F(F(x))$ is not equal to $4x+3$. $F(F(x))=f(f(f(f(x))))$ from your definition of $F$.
mdhasib wrote:then we will get F(x)=2x+1 or F(x)=-2x-3. Considering the next statement we can be sure that F(x)=2x+1.
How do you deduce that? And which statement do you refer to.
mdhasib wrote:Hence F(2015)=(2*2015)+1=4031 :D :D :D :D
You are supposed to fiind out $f(x)$, not $F(x)$.

Also try to write equations in $\LaTeX$. It's not that hard. Write all the maths at https://www.codecogs.com/latex/eqneditor.php, copy paste the code and enclose them by two dollar signs($$).

mdhasib
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Re: 2015 regional Secondary no. 6 function algebra

Unread post by mdhasib » Wed Jan 11, 2017 4:52 pm

thank you for pointing out my mistakes asif vai though i can not edit it . But i was trying to mean f(x) by F(x) and i didnt think of it as a problem and by the next statement i meant f(5^k)=((5^k)*(2^(k-2)))+2^(k-3). I didnt mention it because it would look hideous .

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