Find the coordinates of the points on the curve y = 2x³ - 3x² - 13x +2 at which the tangents to the curve make angles of 135* with the positive sense of the x axis.

edit: I can differentiate the first part and get the slope, 6x² - 6x -13 and solve for x, but I don't get what I am supposed to do with the 135* angle part, I get that the x will be positive but do I just solve for x . Could someone explain the 135* angle part?