"Abscissas" means *x*-values, while "ordinates" means *y*-values.

So the question means "where on the rectangular system do we have *x* = *y* for all points (*x*, *y*)?"

In other words, we want a line connecting points like `(-3, -3)` and `(0, 0)` and `(5, 5)` and `(700, 700)`.

The line we want cuts the first and third quadrants in half at `45^@`. We can write this line as *y* = *x*.

`y=x`