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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,062

let

and f(1)=2,f(2)=5,f(3)=10,f(4)=17, Then find product of digits of f(5).p.s. I am getting f(5)=26 and hence the answer 2*6=12 but unfortunately it's not the correct answer.Help!

friendship is tan 90°.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi;

I am getting f(5)=50.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**math9maniac****Member**- From: Tema
- Registered: 2015-03-30
- Posts: 414

Hi niharika_kumar;

After solving the four equations simultaneously, we have a = -10, b = 36, c = -50 and d = 25. When you substitute these values into f(x) and put f(5), the result is 50 and 5 * 0 we know is zero. There you are!

Try solving again and this should be your answer. Probably take your time with simplifying the equations.

Thanks for sharing the question. Helped me challenge myself.

Only a friend tells you your face is dirty.

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**math9maniac****Member**- From: Tema
- Registered: 2015-03-30
- Posts: 414

Also remember the required equation must satisfy all the values at the same time.

Only a friend tells you your face is dirty.

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**math9maniac****Member**- From: Tema
- Registered: 2015-03-30
- Posts: 414

Also remember the required equation must satisfy all the values at the same time.

Only a friend tells you your face is dirty.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi;

Her answer although incorrect in this context is actually clever and in no way inferior to the requested answer of 50.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,062

Got it but with patience.

thank you math9maniac and bobbym.

friendship is tan 90°.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

26 would be the answer to a simpler fit x^2 + 1 but the question does not ask for it, so 50.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**niharika_kumar****Member**- From: Numeraland
- Registered: 2013-02-12
- Posts: 1,062

yes I did that.

friendship is tan 90°.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

I hope you did the 26 answer using the short way.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**math9maniac****Member**- From: Tema
- Registered: 2015-03-30
- Posts: 414

You're most welcome niharika_kumar. I'm glad you succeeded.

Only a friend tells you your face is dirty.

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