Question

Aratati ca , daca a,b,c sunt invers proportionale cu 1 supra 2, 1 supra 3 si 1 supra 5 , atunci c=a+b.

Answer 1

a*1/2 = b*1/3 = c*1/5 ⇔ a/2 = b/3 = c/5 ⇒ 
a=2c/5
b=3c/5
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a+b= 1/5(2c+3c) = 5c/5 = c cctd(qed)