Which of the following is a complex number?
-7, 2 + √3, 4 + 9i, π

Solution:

Given -7, 2 + √3, 4 + 9i, π

-7 is an integer clearly,

 2 + √3 is a surd

π is an irrational number extending to infinity.

All these are real numbers.

4 + 9i is an imaginary number as it has the imaginary term ‘i’ in it.

A complex number is in the form a + ib

Which of the following is a complex number?

Summary:

4 + 9i is a complex number from the following -7, 2 + √3, 4 + 9i, π.