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Calculeaza 1/radical 2 + radical 1 + 1/radical 3 + radical 2 +...+ 1/ radical 100+ radical 99

Răspuns :

1/(√2 + √1) + 1/(√3 +√2) +...+ 1/(√100+ √99)=
=(√2-√1)/(√2+√1)(√2-√1)+(√3-√2)/(√3+√2)(√3-√2)+....
+(√100-√99)/(√100+√99)(√100-√99)=
=(√2-√1)/(2-1)+(√3-√2)/(3-2)+....+(√100-√99)/(100-99)=
=√2-√1+√3-√2+....+√100-√99=
=-1+10=9