HELP with a calculus problem dealing with tangent lines to a function!?

consider the parabola y=x^2 a) show that the line through the point (3, -7) with a slope -2 is tangent to the parabola. b) find another line through (3, -7) that is tangent to the parabola. c) is there a third line through (3, -7) that is tangent to the parabola? justify your answer. if you could show me step by step how to solve this problem that would be great!! thank you so much!