So it's mentioned that the line is parallel, hence their gradient are equals.
From the eqn, y = 2x + 1 , you'll find that the gradient is 2 (conveniently, the equation of the line is directly derived from y=mx+c, where m is the gradient.)
Using the coordinates (2, -1) as the line passes through those points, make a new equation (with y=mx+c) with those points and the gradient 2 in order to find constant c.
-1=(2)(2) + c c=-5
hence, the equation is y=2x-5.
The whole working is actually very short so I hope I didn't overcomplicate things :(
