Help please I can’t find the answer!

-5

A function is where each input is related to exactly one output. Because -5 was already previously listed as an x value in an ordered pair, it can not be used in a function. Another way of thinking of a function is if it passes the vertical line test where a vertical line can only pass through your line once. Let me know if this doesn't make sense!

introduction, methodology, results, discussion

step-by-step explanation:

an observational study is one which consists of actual observation to record data and then analyse the data.

there are a number of factors that should be analyzed before starting an observational study.

the main four factors are:

i) introduction:   this should be analysed to check whether the purpose of the study is correctly established and the data recorded are appropriate for the study

methodology:   the method of collecting the data, such as whether randomly selected, and whether sample size matches with the population to be studied, whether questions asked are easy to answer by common men, etc.

results: then results such as summary of data with comments should be studied thoroughly

discussion:   the last is the discussion, this can be either by management people or persons who are all interested , etc.