Can somebody explain how to find the answer? I'm confused.

Answer:
f(5a + 1) = [tex]\frac{5a+7}{25a^2+10a+2}[/tex]
Step-by-step explanation:
Given function is,
[tex]f(x)=\frac{x+6}{x^2+1}[/tex]
we have to determine the function when x = (5a + 1)
By substituting the value of x in the given function.
f(5a + 1) = [tex]\frac{(5a+1)+6}{(5a+1)^2+1}[/tex]
= [tex]\frac{5a+7}{(25a^2+10a+1)+1}[/tex] [Since (a + b)² = a² + 2ab + b²]
= [tex]\frac{5a+7}{25a^2+10a+2}[/tex]
Therefore, f(5a + 1) = [tex]\frac{5a+7}{25a^2+10a+2}[/tex] will be the answer.