If the square root of t is a real number, is the square root of t positive?(1) t＞0(2) t2＞0
题目
If the square root of t is a real number, is the square root of t positive?
(1) t＞0
(2) t2＞0
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参考答案和解析
正确答案：E
E 解析：This question is looking for a definite yes or no answer. Statement (1) is not sufficient since all it tells us is that t is a positive number. Unless the radical sign (
) is used, a positive number has two square roots, a positive root and a negative root. For example, if t is 4, then it has two square roots, 2 and -2. So we can eliminate A and D.
With statement (2) alone, we don't get much more information; all it really tells us is that t is a positive number (it cannot be negative, since the square root of a negative number is a complex number, not a real number). So again, t could be 4, and its root could be either positive or negative. So we can eliminate B. Putting them both together doesn't tell us whether the square root of t is positive either, so our answer has to be E.
E 解析：This question is looking for a definite yes or no answer. Statement (1) is not sufficient since all it tells us is that t is a positive number. Unless the radical sign (
) is used, a positive number has two square roots, a positive root and a negative root. For example, if t is 4, then it has two square roots, 2 and -2. So we can eliminate A and D.With statement (2) alone, we don't get much more information; all it really tells us is that t is a positive number (it cannot be negative, since the square root of a negative number is a complex number, not a real number). So again, t could be 4, and its root could be either positive or negative. So we can eliminate B. Putting them both together doesn't tell us whether the square root of t is positive either, so our answer has to be E.