Question

what x value would result in a Y value of 80?

Answer 1

As the rule is: y is equal to one less than x squared:

$y=x^2-1$

For a value of y=80

$\begin{gathered} 80=x^2-1 \\ 80+1=x^2-1+1 \\ 81=x^2 \\ \sqrt[]{81}=x \\ 9=x \end{gathered}$The x value for y=80 is: x=9