# Math Help - using definition of one-to-one

1. ## using definition of one-to-one

Show the function y=2x^2-4x-5 is one-to-one using the definition of one-to-one.

Thank you for helping!

2. A function f(x) is one to one if for $x_1,x_2$ with $x_1\not = x_2$ $f(x_1)\not = f(x_2)$

So 0 doesn't equal 2,

And yet $f(0)=2(0)^2-4(0)-5=-5$

And $f(2)=2(2)^2-4(2)-5=8-8-5=-5$
So therefore your function is not one to one