The question is: Find the equations of the tangent lines to the curve y = 2x^2 + 3 That pass through the point (2, -7)

The last time I did this sort of questions was over a year ago and I think I remember that you're supposed to pick a point (a, f(a) ) on the parabola first, and go from there. But what then? How would you find the slope from (2, -7) to a point you don't know?