binomial

if (9+4√5)n=p+β where n and p are postive integers and β is a positive proper fraction, prove that (1-β)(p+β)=1 ?

4 Answers

62
Lokesh Verma ·

hint look at

(9-4√5)n

can you say that it is less than 1?

1
INDRAJIT Ghosh ·

yes if n=1 then it is less than one.so?

1
INDRAJIT Ghosh ·

pls solve the sum...

62
Lokesh Verma ·

if (9+4√5)n=p+β where n and p are postive integers and β is a positive proper fraction, prove that (1-β)(p+β)=1 ?

(9-4√5)n<1 because (9-4√5)<1 and n is a +ve integer.

also note that
S=(9-4√5)n+(9+4√5)n (let)
S will be an integer.

(9+4√5)n = S - (9-4√5)n
(9+4√5)n = S-1+ {1-(9-4√5)n}

Thus, β={1-(9-4√5)n}

1-β=(9-4√5)n
also, p+β=(9+4√5)n (from above)

Multiply the two, we get
(1-β)(p+β)=1

:)

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