"Tangency" means that there is always only one intersection point between a straight line and a curve on this plane. This point is called the tangent point. The equation describing this straight line is the tangent equation of this curve.
A curve has countless tangents, but not many meet specific requirements. We can establish a linear equation according to our needs, connect it with a curve equation to form an equation group, find out the linear parameters (slope and intercept) that make the solution of the equation group unique, and then get the tangent equation.