For example, lets say the function of the curve is y = x^3
How would you find two lines that pass through points (2, 8) and are tangent to the curve?
It's possible that there's only one tangent that goes through that line and is tangent to the curve, but anyway...
Your tangent is a line, so is of the form y = mx + c.
The gradient of this tangent will be the same as the gradient of the curve at a point. The gradient of the curve at any point is given by the derivative.
So differentiate y = x^3 to get the derivative, and substitute this derivative (as a function of x) as m.
Can you get to there? Can you see what to do next?