??? " " and " " are just two different functions. Whatever methods you learned or " work just as well for ! is completely separate from and has nothing to do with it.
" " here is a linear function (its graph is a straight line) such that and [tex]r_2(1)= (0, 0). Notice that the (x, y) coordinates of the first point are the same, x= y= 1, and of the second point are the same, x= y= 0. Because this is a "linear function", that will always be true- that's why they have "y= x" after the boxes. Now, any linear function can be written as x= at+ b for numbers a and b. If x= 1 when t= 0 and x= 0 when t= 1, what must a and b equal?