Which of the following is not an irrational numbera) 7√5c) (√7 – 3) - ...
Understanding Irrational Numbers
Irrational numbers are real numbers that cannot be expressed as a fraction of two integers. They have non-repeating and non-terminating decimal expansions. Let's analyze the given options to identify which one is not an irrational number.
Option Analysis
- a) 7√5
- The square root of 5 is irrational.
- Multiplying an irrational number by a rational number (7) remains irrational.
- Therefore, 7√5 is irrational.
- b) 2√2 + 2
- The square root of 2 is irrational.
- When multiplied by 2, it remains irrational (2√2).
- Adding 2 (a rational number) to an irrational number (2√2) results in an irrational number.
- Thus, 2√2 + 2 is irrational.
- c) (√7 - 3)
- The square root of 7 is irrational.
- Subtracting a rational number (3) from an irrational number (√7) keeps the result irrational.
- Therefore, (√7 - 3) is irrational.
- d) 2√3 + 2
- The square root of 3 is irrational.
- Multiplying by 2 gives 2√3, which is irrational.
- Adding 2 (a rational number) to an irrational number (2√3) results in an irrational number.
- Thus, 2√3 + 2 is irrational.
Conclusion
All options a), b), c), and d) are irrational numbers. However, if we were to evaluate the entire expression in option b), we find that it can be rewritten as a decimal approximation, which could suggest rationality under certain conditions. Nonetheless, all choices involve irrational components.
Since the question asks for one that is not, it is important to note that all provided answers are indeed irrational numbers.
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