Several factors can be responsible, including: 1  Heredity: If your dad had oily hair, chances are you will, too. 2  Hormonal fluctuations: In adult women, it may come with the menstrual cycle or using birth control pills. 3  Bulking up: Excessive oil is a side effect of using androgenic hormones to increase body mass.
At first glance, a function looks just like a relation. 1  It's a set of ordered pairs such as { (0,1) , (5, 22), (11,9) }. 2  Like a relation, a function has a domain and range made up of the x and y values of ordered pairs.
A function is a relation between two sets defined in such a way that for each element in the first set, the value that corresponds to it in the second set is unique. Let f be a function defined from the set A into set B. Then for each x Ïµ A, the symbol f (x) denotes the unique value in the set B that corresponds to x. It is called the image of x under f. Therefore, a relation f from A into B is a function, if and only if for, each xÏµ A and y Ïµ A; if x = y then f (x) = f (y). The set A is called the domain of the function f, and it is the set in which the function is defined. For example, consider the relation f from R into R defined by f (x) = x + 2 for each xÏµ A. This is a function whose domain is R, as for each real number x and y, x = y implies f (x) = x + 2 = y + 2 = f (y).