Write equation for the line with a slope "undefined" and has the same x-intercept as x−y−1=0

Step-by-step explanation:

Lines with undefined slopes are perfectly vertical, of the form "x = ". A line with "the same x-intercept" as the given line that has an undefined slope will be the line that we want. I know that sounds confusing; we'll work through it then I'll explain it better. In order to find the x-intercep of the given line, solving it for y will make it a bit easier to "see". Therefore,

-y = -x + 1 and

y = x - 1. The x-intercept exists when y = 0, so setting y equal to 0 and solving for x:

0 = x - 1 and

1 = x. That's the x-intercept. It's also the line that we want that has an undefined slope, because "x = " lines are lines vertical lines and vertical lines have undefined slopes.

x = 1 is the line you want.

a. is correct