Răspuns:
A = {7}
Explicație pas cu pas:
U = {0,1,2,3,4,5,6,7,8,9}
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A={x ∈ U |√(1x28)/3 ∈ N}
Elemente posibile :
√(1028/3) ∉ N ; √(1128/3) = √376 ∉ N ; √(1228/3) ∉ N ;
√(1328/3) ∉ N ; √(1428/3) = √476 ∉ N ; √(1528/3) ∉ N
√(1628/3) ∉ N ; √(1728/3) = √576 = 24 ∈ N
√(1828/3) ∉ N ; √(1928/3) ∉N =>
A = {7}