Math Is Fun Forum

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

It's only a quadratic; why can't I do it?

I'm stuck on Q1 from

http://www.mathisfunforum.com/viewtopic.php?id=19669

Somebody join in please and either tell me where I've gone wrong, or do the question.  I'll settle for either.  It's kinda lonely being all on my own there.

Thank you so much

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: It's only a quadratic; why can't I do it?

Hi Bob

Well, doesn't a=b=c imply the property we want proven?

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

Re: It's only a quadratic; why can't I do it?

Well yes, it does.  But surely that can't be it alone.  It's a bizarre way to ask that, isn't it?

Bob

ps.  I suppose there may be many complex solutions.  The other questions suggest the student knows what these are and even if not,  the required property may drop out anyway because you're not asked for the solutions; only to show that result.  What's bothering me is, I can't get that result.

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: It's only a quadratic; why can't I do it?

I still don't get it. There is no mistake in your proof and your last post there proves that it must be that all three are equal...

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

Re: It's only a quadratic; why can't I do it?

Well thanks for helping.  It's nice to know you agree with me.  But how to prove the result?????

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: It's only a quadratic; why can't I do it?

I think the exact wording would help. If a, b and c must be real, then your proof is the whole proof of the result.

---

“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.