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media aritmetica a+b=20 media geometrica=4
 2(1/a+1/b)=?


Răspuns :

a+b=20 ; a*b=4 =>
 a=4/b =>
4/b+b-20=0 => b*b-20b+4=0;
Delta=400-4*4*1= 384;
b1=(20+19.59)/2=19.79; => a=4/19.79=0.2021
b2=(20-19.59)/2=0.205;  => a=4/0.205=19.5121