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Functions. Section 1.4. Relation. The value of one variable is related to the value of a second variable A correspondence between two sets
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Functions Section 1.4
Relation • The value of one variable is related to the value of a second variable • A correspondence between two sets • If x and y are two elements in these sets and if a relation exists between x and y, then xcorresponds to y, or ydepends onx, written xy • x is the input to the relation and y is the output of the relation
Ways to Express Relations • Equations • Graphs • Mapping • Use a set of inputs and draw arrows to the corresponding element in the set of outputs • See page 31
Function • A relation that associates with each element of a domain exactly one element in the range (called the value or image) • Denoted by letters such as f, F, g, G, etc. • To determine if a relation is a function, solve equation for y • More than one solution for y: not a function • Otherwise it’s a function
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Find the Value of a Function • f(x) • f of x • f at x • The value of f at the number x • x is the independent variable (argument) • y is the dependent variable
For the function f defined byf(x) = x2 + 4x, evaluate (A) f(3) (B) f(x) + f(3) (C) f(-x)
For the function f defined byf(x) = x2 + 4x, evaluate (D) -f(x) (E) f(x + 3)
When a function is defined by an equation in x and y, the function f is given implicitly.If it’s possible to solve the equation for y in terms of x, write y = f(x), which means the function is given explicitly.
Find the Domain of a Function • The domain of f is the largest set of real numbers for which the value f(x) is a real number. • If x is in the domain of a function, f is defined at x, or f(x) exists. • If x isn’t in the domain of a function,f is not defined at x, or f(x) does not exist.
Sum of two functions Difference of two functions
Product of two functions Quotientof two functions
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page 44(48, 52, 56, 58, 62-70 even, 73-78)============================pages 44-45(50, 54, 60, 80, 82, 84, 86, 87, 89)