2 x - 6*x - 7 >= 0
x^2 - 6*x - 7 >= 0
Or(And(7 <= x, x < oo), And(x <= -1, -oo < x))
((7 <= x)∧(x < oo))∨((x <= -1)∧(-oo < x))
(-oo, -1] U [7, oo)
x in Union(Interval(-oo, -1), Interval(7, oo))