which of the following is an example of a complex number that is not in the set of real numbers?\n-7\n2 +…

Explanation:

Step1: Recall complex - number definition

A complex number is of the form $a + bi$, where $a,b\in\mathbb{R}$ and $i=\sqrt{- 1}$. A real number is a complex number with $b = 0$.

Step2: Analyze each option

• Option 1: $-7=-7 + 0i$, it is a real number.
• Option 2: $2+\sqrt{3}=2+\sqrt{3}+0i$, it is a real number.
• Option 3: $4 + 9i$ is in the form $a+bi$ with $a = 4$, $b = 9\neq0$, so it is a non - real complex number.
• Option 4: $\pi=\pi+0i$, it is a real number.

Answer:

C. $4 + 9i$