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Infernodragon1
a fost răspuns

r×r+648=7×100+20×10+3×3

Răspuns :

Marianmihalcut34
r^2+648=909
r^2=261
r~16,15

Cocirmariadenis

r × r + 648 = 7 × 100 + 2 × 10 + 3 × 3

r × r + 648 = 700 + 20 + 9

r × r + 648 = 729

r × r = 729 - 648

r × r = 81 ⇒   r = 9 ;    9 x 9 = 81

Raspuns:    r = 9