How can u tell if a function is a "one to one function" ???? so confused as to what this even means?

one-to-one means that each output is associated with exactly one input. For example, y=x^2 would not be one-to-one because the input values (the x's) share y values (e.g. 1 and -1 share 1). When looking at a graph, it is like using the vertical line test to determine if an equation is a function, only you are doing a "horizontal line test." Simply, the x values have to have different y values. Any parabola, like f(x)=x^2+8x+1, is not one-to-one.