For example: y = x2 If 2 is substituted in for x y = 4; if -2 is substitute for x y = 4
Therefore y = 4 has two x values associated with it x = 2 and x = -2. expression in ordered pair notation (2,4),(-2,4)
Every y value in the parabola y = x2 as seen in the below graph will have two x values.
Another example is if x = 3 y = 9 and if x = -3 y still = 9 (3,9),(-3,9)
IMPORTANT - There are functions where every y value has only one x value assigned to it and each x value has only one y value. These are called one to one functions.
For example y = x3 is a one to one function. If 2 is substituted in for x y = 8; if -2 is substitute for x y = -8 (2,8),(-2,-8)
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