Example 1 Given the proposition : The equation has a solution in ; proposition : There is only one real number that satisfies the inequality . If the proposition “ or ” is false, find the range of values for .
Solution
Solve: From we get .
Obviously or .
Since , thus or , so .
There is only one real number satisfying , which means the parabola intersects the -axis at only one point, so , thus or 2.
The proposition “ or ” is true when or .
Since the proposition “ or ” is false, the range of values for is or .
Comment: This problem can also be solved by first using a truth table to determine that both and are false propositions, and then solving the problem.
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