Question

If a decimal has a line over it is it considered negative

Answer 1

No, it means that the number it is over is repeating.

Answer 2

it's called a vinculum it signifies a repeeting group
no if a decimal has a vinculum over it it is a repeeting decimal so
1/3=0.333333333333333333333 or
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0.3 (3 has a vinculum over it)

or

0.345345345345345 is also
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0.345 (345 has a vinculum over it)
it could be negative but