Which one of the following is not an irrational number?

• A) 5 - √3
• B) 5 + √3
• C) 4 + √2
• D) 5 + √9

To determine which option is not an irrational number, let's analyze each choice:

Options Breakdown

• A) 5 - √3: This is irrational because √3 is irrational, and subtracting an irrational number from a rational number (5) results in an irrational number.
• B) 5 + √3: Similar to option A, this is also irrational for the same reason; adding an irrational number to a rational number yields an irrational result.
• C) 4 + √2: Again, this is irrational since √2 is irrational, and adding it to the rational number 4 keeps it irrational.
• D) 5 + √9: Here, √9 equals 3, which is a rational number. Therefore, 5 + 3 equals 8, a rational number.

Final Answer

The option that is not an irrational number is D) 5 + √9.