What is a Parrel line?

Asequence is defined recursively using the formula f(n + 1) =f(n) - 5. which sequence could be

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)

Rachel is studying the population of a particular bird species in a national park. she observes every 10th bird of that species that she can find in the park. her conclusion is that the birds living in the park who belong to that species generally feed on insects. rachel's sample is . based on the sample she picked, rachel's generalization is . reset next