Răspuns
(30/900 - 3/900)² = ( 1/30 - 1/300) ² = 1/900 - 2*1/30*1/300 + 1/90000
1/900 - 2/9000 + 1/90000
amplific prima fractie cu 100 si pe a 2 a cu 10
(100 - 20 + 1) /90000 = 81/90000 = 9/10000