A complex number has a real and an imaginary part
[tex]4 + 9i[/tex] is a complex number
A complex number is represented as:
[tex]a + bi[/tex]
Where:
[tex]a \to[/tex] real
[tex]bi \to[/tex] imaginary
By comparing the options to [tex]a + bi[/tex];
[tex]-7[/tex] and [tex]2 + \sqrt 5[/tex] are not complex numbers
This is so because they do not have imaginary parts
However,
[tex]4 + 9i[/tex] is a complex number
Because; 9i is imaginary
Read more about complex numbers at:
https://brainly.com/question/19007885
