About tangency, we must first make clear three sentences: the tangent point is on the tangent line, the tangent point is on the curve, and the derivative at the tangent point is equal to the slope of the tangent line.

In this question, the slope of tangent can be obtained by substituting the abscissa of tangent point into derivative function, and the ordinate of tangent point can be obtained by substituting the abscissa of tangent point into parabolic equation. Because the tangent point is on the tangent line, the slope can be found, so the tangent equation can be written.