SOLUTION: find the largest interval d on which the formula f(x)=x^2 defines a one to one function solution

   





A function will pass the vertical line test (i.e. a vertical line cuts the graph of the function at most once).



A one-to-one function will ALSO pass the horizontal line test, where any horizontal line drawn cuts the graph of the function at most once.



By eliminating the negative numbers from the domain, f(x)= now passes the horizontal line test.