Question

Show that the function f : R → R, defined as f(x) = x2, is neither one-one nor onto

Answer 1

let f(x)= y
so y = x²
so x = +√y or x = - √y
so we see that for every value of x there are two values of y so it is sure that it is not one-one function 
this function creates a graph which is a parabola which gives us the conclusion that it also not a onto function.