4×0.(4)=4×4/9=16/9=(4/3)²
40×0.0(4)=4×0.(4)=(4/3)²
400×0.00(4)=4×0.(4)=(4/3)²
Deci toti radicalii sint egali intre ei si fiecare are valoarea rad[(4/3)²]=4/3
Acum:
x=25×3×4/3=25×4=100=10²
Deci x este un numar natural patrat perfect.
