Sum of coefficients

This is easy, but looks more in the JEE league:

Its known that a2005+b2005 can be expressed as a homogenous polynomial in (a+b) and ab.

What is the sum of these coefficients?

9 Answers

62
Lokesh Verma ·

1?

62
Lokesh Verma ·

Not for odds but you are pretty close..

a hint is that you have to simply substitute a+b= something and ab=something (else?)

to find the sum of the coefficients [1]

have i given out too much ? :D

62
Lokesh Verma ·

a3+b3=(a+b)3-3ab(a+b)

Here the sum of coefficients is not 1 but -2

Now think a bit more ;)

1
b_k_dubey ·

does it have to do something with cube roots of unity ;)

62
Lokesh Verma ·

does it :P

1
b_k_dubey ·

it does :D

for odd integers non-multiples of 3 it will be 1

for odd integers multiples of 3 sum of coefficients will be -2

62
Lokesh Verma ·

arrey yaar this question is not for us :P

[3] i was only trying to confuse the users here.. (you are giving away way too much ;)

1
akari ·

here is the solution
took a hell lot of hint from dubey sir ;)


now

if we put
a+b=1
and
ab=1
hence
a=
b=
we will get

the l.h.s becomes

62
Lokesh Verma ·

why did you hide it ..

This is correct..

good work :)

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