show that :-
If a > 1, then a² < a.
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Remember that:
(a+b)2=a2+2ab+b2(a+b)2=a2+2ab+b2
and
log(a)+log(b)=log(ab)log(a)+log(b)=log(ab)
So,
a2+b2=7aba2+b2=7ab
Adding 2ab2ab on both sides :
a2+b2+2ab=7ab+2aba2+b2+2ab=7ab+2ab
(a+b)2=9ab(a+b)2=9ab
a+b=9ab−−−√=9–√⋅ab−−√=3ab−−√a+b=9ab=9⋅ab=3ab
a+b=3ab−−√a+b=3ab
Multiply by 1313 on both sides :
13(a+b)=13⋅3ab−−√13(a+b)=13⋅3ab
13(a+b)=ab−−√=(ab)1213(a+b)=ab=(ab)12
13(a+b)=(ab)1213(a+b)=(ab)12
Log on both sides :
log(13(a+b))=log((ab)12)=12log(ab)log(13(a+b))=log((ab)12)=12log(ab)
But 12log(ab)=12(log(a)+log(b))12log(ab)=12(log(a)+log(b)) . So,
log(13(a+b))=12(log(a)+log(b))log(13(a+b))=12(log(a)+log(b))
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