Inverse of a Function In this Post I will discuss the method for finding the inverse of a given function from the 4 options as given in the Entrance tests of Engineering Universities. The very first step before finding the inverse is to make a check whether the function is One-to-One or not. By One-to-One function we mean that function for example f(x) should not have the same value at two different values of x. In other words for each element of the Domain there should be a distinct element in the range. Check for One-to-One: A function which passes the horizontal line test is a One-to-One function. This means if a horizontal line is drawn it should not cross the function curve at more than one point. Another way to check if a function is One-to-One or not is shown below: If , f(a) = f(b) , implies that a=b , the given function is One-to-One. Consider the following examples: f(x) = 5x + 10 f(a) = 5a + 10 f(b) = 5b + 10 Taking f(a) = f(b) gives, 5a + 10 = 5a - 10 this means a=b Thus t