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What is the inverse of the function f(x)=2x+1

What is the name used to describe a graph where for some value of x, there exists 2 or more different values of y?

Part a: sam rented a boat at $225 for 2 days. if he rents the same boat for 5 days, he has to pay a total rent of $480. write an equation in the standard form to represent the total rent (y) that sam has to pay for renting the boat for x days. (4 points)