Answer :
Answer:
[tex]\large\text{$26$ is the correct answer.}[/tex]
Step-by-step explanation:
[tex]\large\text{You may use the formula $(a-b)(a+b)=a^2-b^2$ here.}[/tex]
[tex]\large\text{$(1+5i)(1-5i)$}\\[/tex]
[tex]\large\text{$=1^2-(5i)^2$}[/tex]
[tex]\large\text{$=1-(-25)$}[/tex]
[tex]\large\text{$=1+25$}[/tex]
[tex]\large\text{$=26$}[/tex]